NOTICE

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products or the technical information.

June 1995

OUTLINE

......................................................................................................

FEATURES

....................................................................................................

BLOCK DIAGRAM

.........................................................................................

APPLICATIONS

.............................................................................................

PIN CONFIGURATION

...................................................................................

PIN DESCRIPTIONS

......................................................................................

ABSOLUTE MAXIMUM RATINGS

...................................................................

RECOMMENDED OPERATING CONDITIONS

.................................................

DC ELECTRICAL CHARACTERISTICS

...........................................................

AC ELECTRICAL CHARACTERISTICS

...........................................................

GENERAL DESCRIPTION

..............................................................................

FUNCTIONAL DESCRIPTIONS

......................................................................

1. Address Mapping

.........................................................................................

2. Register Settings

.......................................................................................

USAGES

......................................................................................................

1. Data Transfer Formats

..................................................................................

2. Configuration of Oscillation Circuit and Correction of Time Count Deviations

...................

3. Oscillation Halt Sensing and Supply Voltage Monitoring

...........................................

4. Alarm and Periodic Interrupt

...........................................................................

5. 32-kHz Clock Output

....................................................................................

6. Typical Applications

.....................................................................................

7. Typical Characteristics

..................................................................................

8. Typical Software-based Operations

...................................................................

PACKAGE DIMENSIONS

..............................................................................

TAPING SPECIFICATIONS

...........................................................................

5C338A

APPLICATION MANUAL

CONTENTS

3-WIRE SERIAL INTERFACE REAL-TIME CLOCK IC

WITH VOLTAGE MONITORING FUNCTION

5C338A

OUTLINE

The R

5C338A are CMOS real-time clock ICs connected to the CPU by three signal lines CE (Chip Enable), SCLK

(Serial Clock), and SIO (Serial Input/Output), and configured to perform serial transmission of time and calendar

data to the CPU. These models incorporate different functional circuits. The periodic interrupt circuit is configured

to generate interrupt signals with six selectable interrupts ranging from 0.5 seconds to 1 month. The 2 alarm

circuits generate interrupt signals at preset times. The oscillation circuit is driven under constant voltage so that

fluctuations in oscillation frequency due to voltage are small and supply current is also small (TYP. 0.35µA at 3

volts). The oscillation halt sensing circuit can be used to judge the validity of internal data in such events as power-

on. The supply voltage monitoring circuit is configured to record a drop in supply voltage below two selectable

supply voltage monitoring threshold settings. The 32-kHz clock output function is intended to output sub-clock

pulses for the external microcomputer. The oscillation adjustment circuit is intended to adjust time counts with

high precision by correcting deviations in the oscillation frequency of the crystal oscillator. These models come in

an ultra-compact 10-pin SSOP (RS5C338A with a height of 1.25mm and a pin pitch of 0.5mm)and 10-pin SSOP-G

(RV5C338A with a height of 1.2mm and a pin pitch of 0.5mm).

FEATURES

· Timekeeping supply voltage ranging from 1.45 to 5.5 volts

· Low supply current: TYP. 0.35µA (MAX. 0.8µA) at 3 volts (at 25°C)

· Only three signal lines (SCLK, SIO, and CE) required for connection to the CPU.

Maximum clock frequency of 2 MHz (with V

of 5 volts)

· Time counters (counting hours, minutes, and seconds) and calendar counters (counting years, months, days, and

weeks) (in BCD format)

· 1900/2000 identification bit for Year 2000 compliance

· Interrupt circuit configured to generate interrupt signals (with interrupts ranging from 0.5 seconds to 1 month) to

the CPU and provided with an interrupt flag and an interrupt halt circuit

· 2 alarm circuits (Alarm_W for week , hour , and minute alarm settings and Alarm_D for hour and minute alarm

settings)

· 32-kHz clock circuit (CMOS output, equipped with a control pin)

· Oscillation halt sensing circuit which can be used to judge the validity of internal data

· Supply voltage monitoring circuit with two supply voltage monitoring threshold settings

· Automatic identification of leap years up to the year 2099

· Selectable 12-hour and 24-hour mode settings

· Built-in oscillation stabilization capacitors (C

and C

)

· High precision oscillation adjustment circuit

· CMOS process

· Ultra-compact 10-pin SSOP (RS5C338A with a height of 1.25mm and size of 6.4

3.5mm)

Ultra-compact 10-pin SSOP-G (RV5C338A with a height of 1.20mm and size of 4.0

2.9mm)

5C338A

BLOCK DIAGRAM

COMPARATOR_W

ALARM_W REGISTER

(MIN,HOUR,WEEK)

ALARM_D REGISTER

(MIN,HOUR)

COMPARATOR_D

TIME COUNTER

(SEC,MIN,HOUR,WEEK,DAY,MONTH,YEAR)

ADDRESS

DECODER

SHIFT REGISTER

INTERRUPT CONTROL

32kHz

OUTPUT

CONTROL

DIVIDER

CORREC

-TION

DIV

OSC

OSCIN

32KOUT
CLKC

OSCOUT

OSC

DETECT

I/O

CONTROL

VSS

SCLK

SIO

VDD

INTR

VOLTAGE

DETECT

PIN CONFIGURATION

32KOUT

SCLK

SIO

VSS

VDD

OSCIN

OSCOUT

CLKC

INTR

· 10-pin SSOP-G, 10-pin SSOP

APPLICATIONS

· Communication devices (multi function phone, portable phone, PHS or pager)

· OA devices (fax, portable fax)

· Computer (desk-top and mobile PC, portable word-processor, PDA, electric note or video game)

· AV components (portable audio unit, video camera,camera, digital camera or remote controller)

· Home appliances (rice cooker, electric oven)

· Other (car navigation system, multi-function watch)

5C338A

PIN DESCRIPTIONS

Pin No. Symbol

Name

Description

Chip Enable Input

The CE pin is used for interfacing with the CPU. Should be held high to allow

access to the CPU. Incorporates a pull-down resistor. Should be held low or open

when the CPU is powered off. Allows a maximum input voltage of 5.5 volts regard-

less of supply voltage.

SCLK

Serial Clock Input

The SCLK pin is used to input clock pulses synchronizing the input and output of

data to and from the SIO pin. Allows a maximum input voltage of 5.5 volts regard-

less of supply voltage.

SIO

Serial Input/Output

The SIO pin is used to input and output data intended for writing and reading in

synchronization with the SCLK pin. CMOS input/output.

INTR

Interrupt Output

The INTR pin is used to output periodic interrupt signals to the CPU and alarm

interrupt signals (Alarm_W, Alarm_D). Disabled at power-on from 0 volts.

Nch. open drain output.

32KOUT

32-kHz Clock Output

The 32KOUT pin is used to output 32.768-kHz clock pulses. Enabled at power-on

from 0 volts. CMOS output. This pin is disabled if the CLKC pin is set to low or

open.

CLKC

Clock Control Input

The CLCK pin is used to control output of the 32KOUT pin. The clock output is

disabled and held low when the pin is set to low or open. Incorporates a pull-down

resistor.

The OSCIN and OSCOUT pins are used to connect the 32.768-kHz crystal oscilla-

tor (with all other oscillation circuit components built into the R

5C338A.)

The VDD pin is connected to the power supply. The VSS pin is grounded.

OSCIN

Oscillation Circuit

OSCOUT

Input/Output

VDD

Positive Power Supply Input

VSS

Negative Power Supply Input

5C338A

RECOMMENDED OPERATING CONDITIONS

(Vss=0V,Topt=40 to +85°C)

Symbol

Item

Conditions

MIN.

TYP.

MAX.

Unit

Supply Voltage

2.0

5.5

CLK

Timekeeping Voltage

1.45

5.5

Oscillation Frequency

32.768

kHz

PUP

Pull-up Voltage

INTR

5.5

ABSOLUTE MAXIMUM RATINGS

Absolute Maximum ratings are threshold limit values that must not be exceeded even for an instant under

any conditions. Moreover, such values for any two items must not be reached simultaneously. Operation

above these absolute maximum ratings may cause degradation or permanent damage to the device. These

are stress ratings only and do not necessarily imply functional operation below these limits.

ABSOLUTE MAXIMUM RATINGS

Symbol

Item

Conditions

Ratings

Unit

Supply Voltage

0.3 to +6.5

Input Voltage 1

SIO

0.3 to V

+0.3

Input Voltage 2

SCLK, CE,CLKC

0.3 to +6.5

Output Voltage 1

SIO, 32KOUT

0.3 to V

+0.3

Output Voltage 2

INTR

0.3 to +6.5

Power Dissipation

Topt=25°C

300

Topt

Operating Temperature

40 to +85

°C

Tstg

Storage Temperature

55 to +125

°C

(Vss=0V)

5C338A

DC ELECTRICAL CHARACTERISTICS

Symbol

Item

Pin name

Conditions

MIN.

TYP.

MAX.

Unit

IH1

"H" Input Voltage

SCLK,CE,CLKC

0.8V

5.5

IH2

"H" Input Voltage

SIO

=2.5 to 5.5V

0.8V

+0.3

"L" Input Voltage

SCLK,CE,SIO,CLKC

0.3

0.2V

"H" Output Current

SIO,32KOUT

0.5V

0.5

OL1

"L" Output Current

INTR

=0.4V

OL2

SIO,32KOUT

=0.4V

0.5

Input Leakage Current SCLK

=5.5V or Vss

µA

=5.5V

DNCE

Pull-down Resistance

120

400

CLKC

Pull-down Resistance

CLKC

0.35

1.0

µA

Input Current

OZ1

Output Off-state

SIO

Vo=5.5V or Vss

µA

Leakage Current

=5.5V

OZ2

INTR

=5.5V

=3V,CE=OPEN

DD1

Standby Current

Output=OPEN

0.35

0.8

µA

32KOUT=Off mode*

DETH

Supply Voltage Monitoring

Topt=30 to +70°C

1.90

2.10

2.30

Voltage ("H")

DETL

Supply Voltage Monitoring

Topt=30 to +70°C

1.45

1.60

1.80

Voltage ("L")

Internal Oscillation Capacitance 1 OSCIN

Internal Oscillation Capacitance 2 OSCOUT

Unless otherwise specified : Vss=0V,V

=3V,Topt=40 to +85°C

1) For standby current for outputting 32.768-kHz clock pulses from the 32KOUT pin, see "USAGES, 7. Typical Characteristics".

5C338A

Symbol

Item

Conditions

2.5V

4.5

Unit

MIN.

TYP.

MAX.

MIN.

TYP.

MAX.

CES

CE Set-up Time

400

200

CEH

CE Hold Time

400

200

CE Recovery Time

µs

SCLK

SCLK Clock Frequency

1.0

2.0

MHz

CKH

SCLK Clock "H" Time

400

200

CKL

SCLK Clock "L" Time

400

200

CKS

SCLK Set-up Time

200

100

Data Output Delay Time

300

150

Data Output Floating Time

300

150

CEZ

Data Output Floating Time

300

150

After Falling of CE

Input Data Set-up Time

200

100

Input Data Hold Time

200

100

AC ELECTRICAL CHARACTERISTICS

Unless otherwisespecified : Vss=0V, Topt=40 to +85°C

Input/output conditions : V

=0.8

, V

=0.2

, V

=0.8

, V

=0.2

, C

=50pF

SCLK

SIO (Write cycle)

SIO (Read cycle)

CKH

CKL

CKS

CES

CEZ

CEH

) For read/write timing, see Paragraph "USAGES, 1.5 Considerations in Reading and Writing Time Data"

5C338A

GENERAL DESCRIPTION

1. Interface with CPU

The R

5C338A are connected to the CPU by three signal lines CE (Chip Enable), SCLK (Serial Clock), SIO (Serial

Input/Output), through which it reads and write data from and to the CPU. The CPU can access when the CE pin is

held high. Access clock pulses have a maximum frequency of 2MHz (at 5 volts), allowing high-speed data transfer

to the CPU.

2. Clock and Calendar Function

The R

5C338A read and write time data from and to the CPU in units ranging from seconds to the last two digits of

the calendar year. The calendar year will automatically be identified as a leap year when its last two digits are a mul-

tiple of 4. Also available is the 1900/2000 identification bit for Year 2000 compliance. Consequently, leap years up to

the year 2099 can automatically be identified as such.

) The year 2000 is a leap year while the year 2100 is not a leap year.

3. Alarm Function

The R

5C338A incorporate an alarm circuit configured to generate interrupt signals to the CPU for output at preset

times. The alarm circuit allows two types of alarm settings specified by the Alarm_W registers and the Alarm_D

registers. The Alarm_W registers allow week, hour, and minute alarm settings including combinations of multiple

day-of-week settings such as "Monday, Wednesday, and Friday" and "Saturday and Sunday". The Alarm_D regis-

ters allow hour and minute alarm settings. Both Alarm_W and Alarm_D signals are output from the INTR pin. The

current alarm settings specified by these two registers can be checked from the CPU by using a polling function..

4. High-precision Oscillation Adjustment Function

The R

5C338A have built-in oscillation stabilization capacitors (C

and C

), which can be connected to an external

crystal oscillator to configure an oscillation circuit. To correct deviations in the oscillation frequency of the crystal

oscillator, the oscillation adjustment circuit is configured to allow correction of a time count gain or loss (up to ±1.5

ppm at 25°C) from the CPU within a maximum range of approximately ±189 ppm in increments of approximately 3

ppm. Such oscillation frequency adjustment in each system has the following advantages:

· Allows timekeeping with much higher precision than conventional real-time clocks while using a crystal oscillator

with a wide range of precision variations.

· Corrects seasonal frequency deviations through seasonal oscillation adjustment.

· Allows timekeeping with higher precision particularly in systems with a temperature sensing function through

oscillation adjustment in tune with temperature fluctuations.

5C338A

5. Oscillation Halt Sensing Function and Supply Voltage Monitoring Function

The R

5C338A incorporate an oscillation halt sensing circuit equipped with internal registers configured to record

any past oscillation halt, thereby identifying whether they are powered on from 0 volts or battery backed-up. As

such, the oscillation halt sensing circuit is useful for judging the validity of time data.

The R

5C338A also incorporate a supply voltage monitoring circuit equipped with internal registers configured to

record any drop in supply voltage below a certain threshold value. Supply voltage monitoring threshold settings can

be selected between 2.1 and 1.6 volts through internal register settings.

The oscillation halt sensing circuit is configured to confirm the established invalidation of time data in contrast to

the supply voltage monitoring circuit intended to confirm the potential invalidation of time data. Further, the supply

voltage monitoring circuit can be applied to battery supply voltage monitoring.

6. Periodic Interrupt Function

The R

5C338A incorporate a periodic interrupt circuit configured to generate periodic interrupt signals aside from

interrupt signals generated by the alarm circuit for output from the INTR pin. Periodic interrupt signals have five

selectable frequency settings of 2Hz (once per 0.5 seconds), 1Hz (once per 1 second), 1/60Hz (once per 1 minute),

1/3600Hz (once per 1 hour), and monthly (the first day of every month). Further, periodic interrupt signals also

have two selectable waveforms of a normal pulse form (with a frequency of 2Hz or 1Hz) and special form adapted to

interruption from the CPU in the level mode (with second, minute, hour, and month interrupts). The register

records of periodic interrupt signals can be monitored by using a polling function.

7. 32-kHz Clock Output Function

The R

5C338A incorporate a 32-kHz clock circuit configured to generate clock pulses with the oscillation frequency

of a 32.768-kHz crystal oscillator for output from the 32KOUT pin. The 32KOUT pin is CMOS output and the output

from this pin is enabled and disabled when the CLKC pin is held high, and low or open, respectively. The 32-kHz

clock output can be disabled by certain register settings. But it cannot be disabled without manipulation of any two

registers with different addresses, to prevent disabling in such events as the runaway of the CPU. The 32-kHz clock

circuit is enabled at power-on, when the CLKC pin is held high.

5C338A

Data

Second Counter

Minute Counter

Hour Counter

P/A

Day-of-week Counter

Day-of-month Counter

Month Counter and Century Bit 19/20

Year Counter

Oscillation Adjustment Register

(0)

Alarm_W (minute register)

Alarm_W (hour register)

WP/A

Alarm_W (day-of-week register)

Alarm_D (minute register)

Alarm_D (hour register)

DP/A

Control Register 1

WALE DALE 12/24 CLEN2 TEST

Control Register 2

VDSL VDET

SCRATCH

XSTP CLEN1 CTFG WAFG DAFG

Address

Register

FUNCTIONAL DESCRIPTIONS

1. Address Mapping

1) All the data listed above accept both reading and writing.

2) The data marked with "" is invalid for writing and reset to 0 for reading.

3) When the XSTP bit is set to 1 in control register 2, all the bits are reset to 0 in oscillation adjustment register 1, control register 1 and control register 2

excluding the XSTP bit.

4) Writing to the oscillation adjustment register requires zero filling the (0) bit.

5C338A

WALE, DALE

Description

Disabling the alarm interrupt circuit (under the control of the settings of the

Alarm_W registers and the Alarm_D registers).

Enabling the alarm interrupt circuit (under the control of the settings of the

Alarm_W registers and the Alarm_D registers)

WALE

DALE

12/24

CLEN2

TEST

WALE

DALE

12/24

CLEN2

TEST

(For writing)

(For reading)

Default settings*

(Default setting)

2. Register Settings

2.1 Control Register 1 (at Address Eh)

) Default settings: Default value means read/written values when the XSTP bit is set to "1" due to power-on from 0 volts or supply voltage drop.

2.1-1 WALE, DALE

Alarm_W Enable Bit and Alarm_D Enable Bit

2.1-2 12/24-hour Mode Selection Bit

12/24-hour Time Display System Selection bit

12/24

Description

Selecting the 12-hour mode with a.m. and p.m. indications.

Selecting the 24-hour mode

Setting the 12/24 bit to 0 and 1 specifies the 12-hour mode and the 24-hour mode, respectively.

Table of Time Digit Indications

24-hour mode

12-hour mode

24-hour mode

12-hour mode

12 (AM12)

32 (PM12)

01 (AM 1)

21 (PM 1)

02 (AM 2)

22 (PM 2)

03 (AM 3)

23 (PM 3)

04 (AM 4)

24 (PM 4)

05 (AM 5)

25 (PM 5)

06 (AM 6)

26 (PM 6)

07 (AM 7)

27 (PM 7)

08 (AM 8)

28 (PM 8)

09 (AM 9)

29 (PM 9)

10 (AM10)

30 (PM10)

11 (AM11)

31 (PM11)

) Setting the 12/24 bit should precede writing time data.

5C338A

2.1-5 CT

, CT

, and CT

1) Pulse Mode : 2-Hz and 1-Hz clock pulses are output in synchronization with the increment of the second counter

as illustrated in the timing chart on the next page.

TEST

Description

Normal operation mode

Test mode

2.1-4 TEST

Test Bit

(Default setting)

The TEST bit is used only for testing in the factory and should normally be set to 0.

Periodic Interrupt Selection Bits

Description

Waveform mode

Interrupt cycle and falling timing

Off ("H")

Fixed at low ("L")

Pulse Mode

2Hz (Duty cycle of 50%)

Pulse Mode

1Hz (Duty cycle of 50%)

Level Mode

Once per 1 second (Synchronized with second counter increment)

Level Mode

Once per minute (at 00 seconds of every minute)

Level Mode

Once per hour (at 00 minutes and 00 seconds of every hour)

Level Mode

Once per month (at 00 hours, 00 minutes, and 00 seconds of first day of every month)

(Default setting)

2.1-3 CLEN2

32-kHz Clock Output Bit 2

CLEN2

Description

Enabling the 32-kHz clock circuit

Disabling the 32-kHz clock circuit

(Default setting)

For the R

5C338A, setting the CLEN2 bit or the CLEN1 bit (D3 in the control register 2) to 0, and the CLKC pin to

high specifies generating clock pulses with the oscillation frequency of the 32.768-kHz crystal oscillator for output

from the 32KOUT pin. Conversely, setting both the CLEN1 and the CLEN2 bit to 1 or CLKC pin to low specifies

disabling ("L") such output.

5C338A

Relation Between the Mode Waveform and the CTFG Bit

· Pulse mode

Approx. 92

CTFG bit

INTR pin

(Increment of second counter)

Rewriting of the second counter

· Level mode

Setting CTFG bit to 0

(Increment of

second counter)

Setting CTFG bit to 0

CTFG bit

INTR pin

(Increment of

second counter)

(Increment of

second counter)

) In the pulse mode, the increment of the second counter is delayed by approximately 92µs from the falling edge of clock pulses. Consequently, time

readings immediately after the falling edge of clock pulses may appear to lag behind the time counts of the real-time clocks by approximately 1 second.

Rewriting the second counter will reset the other time counters of less than 1 second, driving the INTR pin low.

2) Level Mode : periodic interrupt signals are output with selectable interrupt cycle settings of 1 second, 1 minute, 1

hour, and 1 month. The increment of the second counter is synchronized with the falling edge of

periodic interrupt signals. For example, periodic interrupt signals with an interrupt cycle setting of

1 second are output in synchronization with the increment of the second counter as illustrated in

the timing chart below.

3) When the oscillation adjustment circuit is used, the interrupt cycle will fluctuate once per 20 seconds as follows:

Pulse Mode : the "L" period of output pulses will increment or decrement by a maximum of ±3.784ms.

For example, 1-Hz clock pulses will have a duty cycle of 50 ±0.3784%.

Level Mode : a periodic interrupt cycle of 1 second will increment or decrement by a maximum of ±3.784ms.

5C338A

VDSL

Description

Selecting the supply voltage monitoring threshold setting of 2.1 volts.

Selecting the supply voltage monitoring threshold setting of 1.6 volts.

2.2-1 VDSL

Supply Voltage Monitoring Threshold Selection Bit

The VDSL bit is intended to select the supply voltage monitoring threshold settings.

VDET

Description

Indicating supply voltage above the supply voltage monitoring threshold settings.

Indicating supply voltage below the supply voltage monitoring threshold settings.

2.2-2 VDET

Supply Voltage Monitoring Result Indication Bit

(Default setting)

Once the VDET bit is set to 1, the supply voltage monitoring circuit will be disabled while the VDET bit will hold the

setting of 1. The VDET bit accepts only the writing of 0, which restarts the supply voltage monitoring circuit.

Conversely, setting the VDET bit to 1 causes no event.

VDSL

VDET

SCRATCH

XSTP

CLEN1

CTFG

WAFG

DAFG

VDSL

VDET

SCRATCH

XSTP

CLEN1

CTFG

WAFG

DAFG

2.2 Control Register 2 (at Address Fh)

(For writing)

(For reading)

Default setting*

SCRATCH

Description

2.2-3 SCRATCH

Scratch Bit

(Default setting)

The SCRATCH bit is intended for scratching and accepts the reading and writing of 0 and 1. The SCRATCH bit will

be set to 0 when the XSTP bit is set to 1 in the control register 2.

(Default setting)

) Default settings: Default value means read/written values when the XSTP bit is set to "1" due to power-on from 0 volts or supply voltage drop.

5C338A

2.2-4 XSTP

Oscillator Halt Sensing Bit

CLEN1

Description

Enabling the 32-kHz clock output

Disabling the 32-kHz clock output

2.2-5 CLEN1

32-kHz Clock Output Bit 1

(Default setting)

CTFG

Description

Periodic interrupt output "H" (OFF)

Periodic interrupt output "L" (ON)

2.2-6 CTFG

Periodic Interrupt Flag Bit

(Default setting)

The CTFG bit is set to 1 when the periodic interrupt signals are output from the INTR pin ("L"). The CTFG bit

accepts only the writing of 0 in the level mode, which disables ("H") the INTR pin until it is enabled ("L") again in

the next interrupt cycle. Conversely, setting the CTFG bit to 1 causes no event.

Setting the CLEN1 bit or the CLEN2 bit (D4 in control register 1) to 0, and the CLKC pin to high specifies

generating clock pulses with the oscillation frequency of the 32.768-kHz crystal oscillator for output from the

32KOUT pin. Conversely, setting both the CLEN1 bit and the CLEN2 bit to 1 or the CLKC pin to low specifies

disabling ("L") such output.

The XSTP bit is for sensing a halt in the oscillation of the crystal oscillator. The oscillation halt sensing circuit

operates only when the CE pin is "L".

· The XSTP bit will be set to 1 once a halt in the oscillation of the crystal oscillator is caused by such events as pow-

er-on from 0 volts and a drop in supply voltage. The XSTP bit will hold the setting of 1 even after the restart of

oscillation. As such, the XSTP bit can be applied to judge the validity of clock and calendar data after power-on or

a drop in supply voltage.

· When the XSTP bit is set to 1, all bits will be reset to 0 in the oscillation adjustment register, control register 1, and

control register 2, stopping the output from the INTR pin and starting the output of 32.768-kHz clock pulses from

the 32KOUT pin.

(32KOUT output is disabled when CLKC pin is set to low.)

· The XSTP bit accepts only the writing of 0, which restarts the oscillation halt sensing circuit. Conversely, setting

the XSTP bit to 1 causes no event.

XSTP

Description

Sensing a normal condition of oscillation

Sensing a halt of oscillation

(Default setting)

5C338A

WAFG, DAFG

Description

Indicating a mismatch between current time and preset alarm time

Indicating a match between current time and preset alarm time

2.2-7 WAFG and DAFG

Alarm_W Flag Bit and Alarm_D Flag Bit

(Default setting)

The WAFG and DAFG bits are valid only when the WALE and DALE bits have the setting of 1, which is caused

approximately 61µs after any match between current time and preset alarm time specified by the Alarm_W registers

and the Alarm_D registers. The WAFG and DAFG bits accept only the writing of 0, which disables ("H") the INTR

pin until it is enabled ("L") again at the next preset alarm time. Conversely, setting the WAFG and DAFG bits to 1

causes no event. The WAFG and DAFG bits will have the reading of 0 when the alarm interrupt circuit is disabled

with the WALE and DALE bits set to 0. The settings of the WAFG and DAFG bits are synchronized with the output

of the INTR pin as shown in the timing chart below.

Output Relationships Between the WAFG or DAFG Bit and INTR

Writing of 0 to WAFG
(DAFG) bit

(Match between current time
and preset alarm time)

Writing of 0 to WAFG
(DAFG) bit

Settings of WAFG (DAFG) bit

Output of INTR pin

Approx. 61

5C338A

2.3 Time Counters (at Addresses 0h to 2h)

· Time digit display (BCD format) as follows:

The second digits range from 00 to 59 and are carried to the minute digit in transition from 59 to 00.

The minute digits range from 00 to 59 and are carried to the hour digits in transition from 59 to 00.

The hour digits range as shown in "2.1-2 12/24: 12-/24-hour Mode Selection Bit" and are carried to the day-of-

month and day-of-week digits in transition from PM11 to AM12 or from 23 to 00.

· Any writing to the second counter resets divider units of less than 1 second.

· Any carry from lower digits with the writing of non-existent time may cause the time counters to malfunction.

Therefore, such incorrect writing should be replaced with the writing of existent time data.

2.3-1 Second Counter (at Address 0h)

Indefinite

(For writing)

(For reading)

Default settings*

2.3-2 Minute Counter (at Address 1h)

Indefinite

(For writing)

(For reading)

Default settings*

2.3-3 Hour Counter (at Address 2h)

P/A or H

Indefinite

(For writing)

(For reading)

Default settings*

) Default settings: Default value means read/written values when the XSTP bit is set to "1" due to power-on from 0 volts or supply voltage drop.

5C338A

2.4 Day-of-week Counter (at Address 3h)

Indefinite

(For writing)

(For reading)

Default settings*

) Default settings: Default value means read/written values when the XSTP bit is set to "1" due to power-on from 0 volts or supply voltage drop.

· The day-of-week counter is incremented by 1 when the day-of-week digits are carried to the day-of-month digits.

· Day-of-week display (incremented in septimal notation):

, W

) = (0, 0, 0)

(0, 0, 1)

...

(1, 1, 0)

(0, 0, 0)

· Correspondences between days of the week and the day-of-week digits are user-definable (e.g. Sunday = 0, 0, 0)

· The writing of (1, 1, 1) to (W

, W

) is prohibited except when days of the week are unused.

2.5 Calendar Counters (at Address 4h to 6h)

· The calendar counters are configured to display the calendar digits in BCD format by using the automatic calen-

dar function as follows:

The day-of-month digits (D

to D

) range from 1 to 31 for January, March, May, July, August, October, and

December; from 1 to 30 for April, June, September, and November; from 1 to 29 for February in leap years;

from 1 to 28 for February in ordinary years.

The day-of-month digits are carried to the month digits in reversion from the last day of the month to 1. The

month digits (MO

to MO

) range from 1 to 12 and are carried to the year digits in reversion from 12 to 1.

The year digits (Y

to Y

) range from 00 to 99 (00, 04, 08, ... , 92, and 96 in leap years) and are carried to the

19/20 digits in reversion from 99 to 00.

The 19/20 digits cycle between 0 and 1 in reversion from 99 to 00 in the year digits.

· Any carry from lower digits with the writing of non-existent calendar data may cause the calendar counters to mal-

function. Therefore, such incorrect writing should be replaced with the writing of existent calendar data.

2.5-1 Day-of-month Counter (at Address 4h)

Indefinite

(For writing)

(For reading)

Default settings*

2.5-2 Month Counter + Century Bit (at Address 5h)

19/20

Indefinite

(For writing)

(For reading)

Default settings*

RS5C338A

2.5-3 Year Counter (at Address 6h)

Indefinite

(For writing)

(For reading)

Default settings*

2.6 Oscillation Adjustment Register (at Address 7h)

(0)

(For writing)

(For reading)

Default settings*

) Default settings: Default value means read/written values when the XSTP bit is set to "1" due to power-on from 0 volts or supply voltage drop.

2.6-1 (0) Bit

The (0) bit should be set to 0 to allow writing to the oscillation adjustment register. The (0) bit will be set to 0 when

the XSTP bit is set to 1 in the control register 2.

2.6-2 F

to F

The oscillation adjustment circuit is configured to change time counts of 1 second on the basis of the settings of the

oscillation adjustment register when the second digits read 00, 20, or 40 seconds. Normally, the second counter is

incremented once per 32768 32.768-kHz clock pulses generated by the crystal oscillator. Writing to the F

to F

bits

activates the oscillation adjustment circuit.

· The oscillation adjustment circuit will not operate with the same timing (00, 20, or 40 seconds) as the timing of

writing to the oscillation adjustment register.

· The F

bit setting of 0 causes an increment of time counts by ((F

, F

) 1)

The F

bit setting of 1 causes a decrement of time counts by (( F

, F

) +1)

The settings of "

, 0, 0, 0, 0, 0,

" ( "

" representing either "0" or "1" ) in the F

, F

, and F

bits

cause neither an increment nor decrement of time counts.

Example:

When the second digits read 00, 20, or 40, the settings of "0, 0, 0, 0, 1, 1, 1" in the F

, F

, and F

bits

cause an increment of the current time counts of 32768 by (71)

2 to 32780 (a current time count loss). When the

second digits read 00, 20, or 40, the settings of "0, 0, 0, 0, 0, 0, 1" in the F

, F

, and F

bits cause neither

an increment nor a decrement of the current time counts of 32768.

When the second digits read 00, 20, or 40, the settings of "1, 1, 1, 1, 1, 1, 0" in the F

, F

, and F

bits

cause a decrement of the current time counts of 32768 by (2)

2 to 32764 (a current time count gain).

) Default settings: Default value means read/written values when the XSTP bit is set to "1" due to power-on from 0 volts or supply voltage drop.

5C338A

2.7 Alarm_W Register (at Address 8h to Ah)

Indefinite

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

(For writing)

(For reading)

Default settings*

2.7-1 Alarm_W Minute Register (at Address 8h)

,WP/A

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

(For writing)

(For reading)

Default settings*

2.7-2 Alarm_W Hour Register (at Address 9h)

Indefinite

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

(For writing)

(For reading)

Default settings*

2.7-3 Alarm_W Day-of-week Register (at Address Ah)

· The D5 bit of the Alarm_W hour register represents WP/A when the 12-hour mode is selected (0 for a.m. and 1

for p.m.). and WH

when the 24-hour mode is selected (tens in the hour digits).

· The Alarm _W registers should not have any non-existent alarm time settings. (Note that any mismatch between

current time and preset alarm time specified by the Alarm_W registers may disable the alarm circuit.)

· When the 12-hour mode is selected, the hour digits read 12 and 32 for 0 a.m. and 0 p.m., respectively (see "2.1-2

12/24: 12-/24-hour Mode Selection Bit").

· WW

to WW

correspond to W

, W

, and W

of the day-of-week counter with settings ranging from (0, 0, 0) to (1,

1, 0).

· WW

to WW

with respective settings of 0 disable the outputs of the Alarm_W registers.

) Default settings: Default value means read/written values when the XSTP bit is set to "1" due to power-on from 0 volts or supply voltage drop.

An increase of two clock pulses once per 20 seconds causes a time count loss of approximately 3ppm (2 / (32768

20=3.051ppm). Conversely, a decrease of two clock pulses once per 20 seconds causes a time count gain of 3ppm.

Consequently, deviations in time counts can be corrected with a precision of ±1.5ppm. Note that the oscillation

adjustment circuit is configured to correct deviations in time counts and not the oscillation frequency of the 32.768-

kHz clock pulses. For further details, see "USAGE, 2.4 Oscillation Adjustment Circuit".

5C338A

Day-of-week

12-hour mode

24-hour mode

Preset alarm time

Sun. Mon. Tue. Wed. Thu.

Fri.

Sat.

10-hour 1-hour 10-min 1-min 10-hour 1-hour 10-min 1-min

00:00 a.m. on all days

01:30 a.m. on all days

11:59 a.m. on all days

00:00 p.m. on

Mondays to Fridays

01:30 p.m. on Sundays

11:59 p.m. on Mondays,

Wednesdays, and Fridays

Note that the correspondence between WW

to WW

and the days of the week shown in the above table is only an

example and not mandatory.

Indefinite

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

(For writing)

(For reading)

Default settings*

2.8-1 Alarm_D Minute Register (at Address Bh)

,DP/A

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

(For writing)

(For reading)

Default settings*

2.8-2 Alarm_D Hour Register (at Address Ch)

2.8 Alarm_D Register (at Address Bh and Ch)

) Default settings: Default value means read/written values when the XSTP bit is set to "1" due to power-on from 0 volts or supply voltage drop.

· The D5 bit represents DP/A when the 12-hour mode is selected (0 for a.m. and 1 for p.m.). and DH

when the 24-

hour mode is selected (tens in the hour digits).

· The Alarm_D registers should not have any non-existent alarm time settings. (Note that any mismatch between

current time and preset alarm time specified by the Alarm_D registers may disable the alarm circuit.)

· When the 12-hour mode is selected, the hour digits read 12 and 32 for 0 a.m. and 0 p.m., respectively (see "2.1-2

12/24: 12-/24-hour Mode Selection Bit").

Example of Alarm Time Setting

5C338A

USAGES

1. Data Transfer Formats

1.1 Timing Between CE Pin Transition and Data Input/Output

The R

5C338A adopt a 3-wire serial interface by which it uses the CE (Chip Enable), SCLK (Serial Clock), and SIO

(Serial Input/Output), pins to receive and send data to and from the CPU. The 3-wire serial interface provides two

types of input/output timings with which the output and input from the SIO pin output and input are synchronized

with the rising and falling edges of the SCLK pin input, respectively, and vice versa. The R

5C338A are configured

to select either one of two different input/output timings depending on the level of the SCLK pin in the low to high

transition of the CE pin. Namely, when the SCLK pin is held low in the low to high transition of the CE pin, the

models will select the timing with which the output and input from the SIO pin are synchronized with the rising and

falling edges of the SCLK pin input, respectively, as illustrated in the timing chart below.

CES

SCLK

SIO

(Input to the real-time clock)

SIO

(Output from the real-time clock)

Conversely, when the SCLK pin is held high in the low to high transition of the CE pin, the models will select the

timing with which the output and input from the SIO pin are synchronized with the falling and rising edges of the

SCLK pin input, respectively as illustrated in the timing chart below.

CES

SCLK

SIO

(Input to the real-time clock)

SIO

(Output from the real-time clock)

5C338A

SCLK

SIO

Setting the address

pointer

Setting the transfer

format register

Writing data transfer /
Reading data transfer

1.2 Data Transfer Formats

Data transfer is commenced in the low to high transition of the CE pin input and completed in its high to low

transition. Data transfer is conducted serially in multiple units of 1 byte (8 bits). The former 4 bits are used to

specify in the address pointer a head address with which data transfer is to be commenced from the host. The latter

4 bits are used to select either reading data transfer or writing data transfer and set the transfer format register to

specify an appropriate data transfer format. All data transfer formats are designed to transfer the most significant bit

(MSB) first.

Two types of data transfer formats are available for reading data transfer and writing data transfer each.

1.3 Writing Data Transfer Formats

1.3-1 1-byte Writing Data Transfer Format

The first type of writing data transfer format is designed to transfer 1-byte data at a time and can be selected by

specifying in the address pointer a head address with which writing data transfer is to be commenced and then

writing the setting of 8h to the transfer format register. This 1-byte writing data transfer can be completed by

driving the CE pin low or continued by specifying a new head address in the address pointer and setting the transfer

format.

Example of 1-byte Writing Data Transfer

(For Writing Data to Addresses Fh and 7h)

1 1 1 1 1

0 1 1 1

0 0

Specifying Fh
in the address
pointer

Writing data
to address Fh

Data

Data transfer from the host

Data transfer from the real-time clocks

SIO

Setting 8h
in the transfer
format register

Specifying 7h
in the address
pointer

Writing data
to address 7h

Setting 8h
in the transfer
format register

5C338A

1.3-2 Burst Writing Data Transfer Format

The second type of writing data transfer format is designed to transfer a sequence of data serially and can be

selected by specifying in the address pointer a head address with which writing data transfer is to be commenced

and then writing the setting of 0h to the transfer format register. The address pointer is incremented for each

transfer of 1-byte data and cycled from Fh to 0h. This burst writing data transfer can be completed by driving the

CE pin low.

Example of Burst Writing Data Transfer

(For Writing Data to Addresses Eh, Fh, and Oh)

1 1 1 0 0

Specifying Eh
in the address
pointer

Writing data
to address Eh

Writing data
to address Fh

Data

Data transfer from the host

Data transfer from the real-time clocks

SIO

Setting 0h
in the transfer
format register

Writing data
to address 0h

1 1 1 0 1

Specifying Eh
in the address
pointer

Reading data
from address Eh

Data transfer from the host

Data transfer from the real-time clocks

SIO

Setting Ch
in the transfer
format register

Specifying 2h
in the address
pointer

Setting Ch
in the transfer
format register

Reading data
from address 2h

Data

0 0 1 0 1

1.4 Reading Data Transfer Formats

1.4-1 1-byte Reading Data Transfer Format

The first type of reading data transfer format is designed to transfer 1-byte data at a time and can be selected by

specifying in the address pointer a head address with which reading data transfer is to be commenced and then the

setting of writing Ch to the transfer format register. This 1-byte reading data transfer can be completed by driving

the CE pin low or continued by specifying a new head address in the address pointer and setting the transfer format.

Example of 1-byte Reading Data Transfer

(For Reading Data from Addresses Eh and 2h)

5C338A

1.4-2 Burst Reading Data Transfer Format

The second type of reading data transfer format is designed to transfer a sequence of data serially and can be

selected by specifying in the address pointer a head address with which reading data transfer is to be commenced

and then writing the setting of 4h to the transfer format register. The address pointer is incremented for each

transfer of 1-byte data and cycled from Fh to 0h. This burst reading data transfer can be completed by driving the

CE pin low.

Example of Burst Reading Data Transfer

(For Reading Data from Addresses Fh, 0h, and 1h)

1 1 1 1 0

Specifying Fh
in the address
pointer

Reading data
from address Fh

Reading data
from address 0h

Data

Data transfer from the host

Data transfer from the real-time clocks

SIO

Setting 4h
in the transfer
format register

Reading data
from address 1h

1 1 1 1 1

Specifying Fh
in the address
pointer

Reading data
from address Fh

Data transfer from the host

Data transfer from the real-time clocks

SIO

Setting Ch
in the transfer
format register

Setting 8h
in the transfer
format register

Specifying Fh
in the address
pointer

Writing data
to address Fh

Data

1 1 1 1 1

1.4-3 Combination of 1-byte Reading and Writing Data Transfer Formats

The 1-byte reading and writing data transfer formats can be combined together and further followed by any other

data transfer format.

Example of Combination of 1-byte Reading and Writing Data Transfer

(For Reading and Writing Data from and to

Address Fh)

The reading and writing data transfer formats correspond to the settings in the transfer format register as shown in

the table below.

1-byte transfer

Burst (Successive) transfer

Writing data transfer

(for writing to real-time clock)

(1,0,0,0)

(0,0,0,0)

Reading data transfer

(for reading from real-time clock)

(1,1,0,0)

(0,1,0,0)

5C338A

Actual time

Time counts within real-time clocks

13:59:59

14:00:00

14:00:01

13:59:59

14:00:00

14:00:01

MAX.61

1.5 Considerations in Reading and Writing Time Data

Any carry to the second digits in the process of reading or writing time data may cause reading or writing erroneous

time data. For example, suppose a carry out of 13:59:59 into 14:00:00 occurs in the process of reading time data in

the middle of shifting from the minute digits to the hour digits. At this moment, the second digits, the minute digits,

and the hour digits read 59 seconds, 59 minutes, and 14 hours, respectively (indicating 14:59:59) to cause the

reading of time data deviating from actual time virtually 1 hour. A similar error also occurs in writing time data. To

prevent such errors in reading and writing time data, the R

5C338A have the function of temporarily locking any

carry of the time digits during the high interval of the CE pin and unlocking such a carry in its high to low transition.

Note that a carry of the second digits can be locked for only 1 second, during which time the CE pin should be

driven low.

The effective use of this function requires the following considerations in reading and writing time data:

(1) Hold the CE pin high in each session of reading or writing time data.

(2) Ensure that the high interval of the CE pin lasts within 1 second. Should there be any possibility of the host

going down in the process of reading or writing time data, make arrangements in the peripheral circuitry as to

drive the CE pin low or open at the moment that the host actually goes down.

(3) Leave a time span of 31µs or more from the low to high transition of the CE pin to the start of access to address-

es 0h to 6h in order that any ongoing carry of the time digits may be completed within this time span.

(4) Leave a time span of 61µs or more from the high to low transition of the CE pin to its low to high transition in

order that any ongoing carry of the time digits during the high interval of the CE pin may be adjusted within this

time span.

(5) The considerations listed in (1), (3), and (4) above are not required when the process of reading or writing time

data is obviously free from any carry of the time digits (e.g. reading or writing time data in synchronization with

the periodic interrupt function in the level mode or the alarm interrupt function).

Good and bad examples of reading and writing time data are illustrated on the next page.

5C338A

SIO

F0h

Data

Time span of 31

s or more

Specifying Fh in the
address pointer
Writing 4h to the
transfer format register

Reading from the
control register 2
at address Fh

Reading from
the second
counter at
address 0h

Reading from
the minute
counter at
address 1h

Reading from
the hour counter
at address 2h

F4h

Data

SIO

Time span of

s or more

Time span of less than 31

Time span of

less than 61

Time span of

s or more

Specifying 0h in the
address pointer
Writing Ch in the
transfer format register

Specifying Fh in the
address pointer
Writing 0h to the
transfer format register

Specifying 0h in the
address pointer
Writing Ch to the
transfer format register

Specifying 1h in the
address pointer
Writing 4h in the
transfer format register

Reading from
the second
counter
at address 0h

Writing to the
control register 2
at address Fh

Reading from
the hour counter
at address 2h

Reading from
the minute
counter
at address 1h

Writing to the
second counter
at address 0h

Reading from the
second counter
at address 0h

Writing to the
minute counter
at address 1h

Writing to the
hour counter
at address 2h

0Ch

Data

14h

SIO

Reading from the
second counter
at address 0h

0Ch

Data

0Ch

Data

Good Example

Bad Example (2) (Where a time span of less than 31

s is left until the start of the process of writing time data)

Bad Example (3) (Where a time span of less than 61

s is left between the adjacent processes of reading time data)

Data transfer from the host

Data transfer from the real-time clocks

Any address other than addresses 0h to 6h
permits of immediate reading or writing
without requiring a time span of 31

Bad Example (1) (Where the CE pin is once driven low in the process of reading time data)

5C338A

2. Configuration of Oscillation Circuit and Correction of Time Count Deviations

2.1 Configuration of Oscillating Circuit

Typical externally-equipped element

X'tal: 32.768kHz

=30k

TYP.)

=6pF to 8pF)

Standard values of internal elements

=15M

TYP.

=120k

TYP.

, C

=12pF TYP.

The oscillation circuit is driven at a constant voltage of approximately 1.2 volts relative to the level of the V

input. As such, it is configured to generate an oscillating waveform with a peak-to-peak voltage on the order of 1.2

volts on the positive side of the V

pin input.

Considerations in Handling Crystal Oscillators

Generally, crystal oscillators have basic characteristics including an equivalent series resistance (R

)

indicating the ease of their oscillation and a load capacitance (C

) indicating the degree of their center

frequency. Particularly, crystal oscillators intended for use with the R

5C338A are recommended to have a

typical R

value of 30k

and a typical C

value of 6 to 8pF. To confirm these recommended values, contact

the manufacturers of crystal oscillators intended for use with these particular models.

Considerations in Installing Components around the Oscillation Circuit

1) Install the crystal oscillator in the closest possible vicinity to the real-time clock ICs.

2) Avoid laying any signal lines or power lines in the vicinity of the oscillation circuit (particularly in the area

marked "

" in the above figure).

3) Apply the highest possible insulation resistance between the OSCIN and OSCOUT pins and the printed

circuit board.

4) Avoid using any long parallel lines to wire the OSCIN and OSCOUT pins.

5) Take extreme care not to cause condensation, which leads to various problems such as oscillation halt.

Other Relevant Considerations

1) For external input of 32.768-kHz clock pulses to the OSCIN pin:

DC coupling: Prohibited due to an input level mismatch.

AC coupling: Permissible except that the oscillation halt sensing circuit does not guarantee perfect

operation because it may cause sensing errors due to such factors as noise.

2) To maintain stable characteristics of the crystal oscillator, avoid driving any other IC through 32.768-kHz

clock pulses output from the OSCOUT pin.

5C338A

OSCIN

OSCOUT

32kHz

VDD

5C338A

2.2 Measurement of Oscillation Frequency

1) The R

5C338A are configured to generate 32.768-kHz clock pulses for output from the 32KOUT pin at power-on conditionally on setting the XSTP bit

to 1 in the control register 2.

2) A frequency counter with 6 (more preferably 7) or more digits on the order of 1ppm is recommended for use in the measurement of the oscillation fre-

quency of the oscillation circuit.

3) The CLKC input should be connected to the V

pin with a pull-up resistor.

2.3 Adjustment of Oscillation Frequency

The oscillation frequency of the oscillation circuit can be adjusted by varying procedures depending on the usage of

the R

5C338A in the system into which they are to be built and on the allowable degree of time count errors. The

flow chart below serves as a guide to selecting an optimum oscillation frequency adjustment procedure for the

relevant system.

Start

Use 32-kHz

clock circuit?

YES

Use 32-kHz clock circuit without regard
to its frequency precision?

Allowable time count precision is on order of oscillation
frequency variations of crystal oscillator *

plus

frequency variations of real-time clock? *

Allowable time count precision is on order of oscillation
frequency variations of crystal oscillator *

plus

frequency variations of real-time clock? *

To Course (A)

To Course (B)

To Course (C)

To Course (D)

1) Generally, crystal oscillators for commercial use are classified in terms of their center frequency depending on their load capacitance (C

) and further

divided into ranks on the order of ±10, ± 20, and ±50 ppm depending on the degree of their oscillation frequency variations.

2) Basically, the R

5C338A are configured to cause frequency variations on the order of ±5 to ±10ppm at normal temperature.

3) Time count precision as referred to in the above flow chart is applicable to normal temperature and actually affected by the temperature characteristics

and other properties of crystal oscillators.

Frequency

counter

5C338A

32.768kHz

OSCIN

OSCOUT

CLKC

VDD

32KOUT

5C338A

Course (A)

When the time count precision of each real-time clock is not to be adjusted, the crystal oscillator intended for use

with that real-time clock may have any C

value requiring no presetting. The crystal oscillator may be subject to

frequency variations which are selectable within the allowable range of time count precision. Several crystal

oscillators and real-time clocks should be used to find the center frequency of the crystal oscillators by the method

described in "2.2 Measurement of Oscillation Frequency" and then calculate an appropriate oscillation adjustment

value by the method described in "2.4 Oscillation Adjustment Circuit" for writing this value to the R

5C338A.

Course (B)

When the time count precision of each real-time clock is to be adjusted within the oscillation frequency variations of

the crystal oscillator plus the frequency variations of the real-time clock ICs, it becomes necessary to correct

deviations in the time count of each real-time clock by the method described in "2.4 Oscillation Adjustment Circuit".

Such oscillation adjustment provides crystal oscillators with a wider range of allowable settings of their oscillation

frequency variations and their C

values. The real-time clock IC and the crystal oscillator intended for use with that

real-time clock IC should be used to find the center frequency of the crystal oscillator by the method described in

"2.2 Measurement of Oscillation Frequency" and then confirm the center frequency thus found to fall within the

range adjustable by the oscillation adjustment circuit before adjusting the oscillation frequency of the oscillation

circuit. At normal temperature, the oscillation frequency of the oscillator circuit can be adjusted by up to

approximately ±1.5ppm.

Course (C)

Course (C) together with Course (D) requires adjusting the time count precision of each real-time clock as well as

the frequency of 32.768-kHz clock pulses output from the 32KOUT pin. Normally, the oscillation frequency of the

crystal oscillator intended for use with the real-time clocks should be adjusted by adjusting the oscillation stabilizing

capacitors C

and C

connected to both ends of the crystal oscillator. The R

5C338A, which incorporate the C

and the C

, require adjusting the oscillation frequency of the crystal oscillator through its C

value.

Generally, the relationship between the C

value and the C

and C

values can be represented by the following

equation:

+ C

where "C

" represents the floating capacity of the printed circuit board

+ C

The crystal oscillator intended for use with the R

5C338A is recommended to have the C

value on the order of 6 to

8pF. Its oscillation frequency should be measured by the method described in "2.2 Measurement of Oscillation

Frequency". Any crystal oscillator found to have an excessively high or low oscillation frequency (causing a time

count gain or loss, respectively) should be replaced with another one having a smaller and greater C

value,

respectively until another one having an optimum C

value is selected. In this case, the bit settings disabling the

oscillation adjustment circuit (see "2.4 Oscillation Adjustment Circuit") should be written to the oscillation

adjustment register.

5C338A

2.4 Oscillation Adjustment Circuit

The oscillation adjustment circuit can be used to correct a time count gain or loss with high precision by varying the

number of 1-second clock pulses once per 20 seconds. When such oscillation adjustment is not to be made, the

oscillation adjustment circuit can be disabled by writing the settings of "

, 0, 0, 0, 0, 0,

" ("

" representing "0" or

"1") to the F

, F

, and F

bits in the oscillation adjustment circuit. Conversely, when such oscillation

adjustment is to be made, an appropriate oscillation adjustment value can be calculated by the equation below for

writing to the oscillation adjustment circuit.

2.4-1 When Oscillation Frequency *

is Higher than Target Frequency *

(There is a Time Count Gain)

Oscillation adjustment value*

(Oscillation frequency Target frequency + 0.1)

Oscillation frequency

3.051

= (Oscillation frequency Target frequency)

10 + 1

1) Oscillation frequency:

Frequency of clock pulses output from the 32KOUT pin at normal temperature in the manner described in "2.2

Measurement of Oscillation Frequency".

2) Target frequency:

Desired frequency to be set. Generally, a 32.768-kHz crystal oscillator has such temperature characteristics as to have

the highest oscillation frequency at normal temperature. Consequently, the crystal oscillator is recommended to have

target frequency settings on the order of 32.768 to 32.76810kHz (+3.05ppm relative to 32.768kHz). Note that the target

frequency differs depending on the environment or location where the equipment incorporating the real-time clocks is

expected to be operated.

3) Oscillation adjustment value: Value that is to be finally written to the F

to F

bits in the oscillation adjustment register and is represented in 7-bit coded

decimal notation.

1) The C

GOUT

should have a capacitance ranging from 0 to 15pF.

Course (D)

It is necessary to select the crystal oscillator in the same manner as in Course (C) as well as correct errors in the
time count of each real-time clock in the same manner as in Course (B) by the method described in "2.4 Oscillation
Adjustment Circuit".

5C338A

OSCIN

OSCOUT

32kHz

GOUT

VDD

Another advisable way to select a crystal oscillator having an optimum C

value is to contact the manufacturer of the

crystal oscillator intended for use with the R

5C338A.

Incidentally, the high oscillation frequency of the crystal oscillator can also be adjusted by adding an external

oscillation stabilization capacitor C

GOUT

as illustrated in the diagram below.

. .

5C338A

Notes

1) Oscillation adjustment does not affect the frequency of 32.768-kHz clock pulses output from the 32KOUT

pin.

2) Oscillation adjustment value range: When the oscillation frequency is higher than the target frequency

(causing a time count gain), an appropriate time count gain ranges from 3.05ppm to 189.2ppm with the

settings of "0, 0, 0, 0, 0, 1, 0" to "0, 1, 1, 1, 1, 1, 1" written to the F

, F

, and F

bits in the

oscillation adjustment register, thus allowing correction of a time count gain of up to +189.2ppm.

Conversely, when the oscillation frequency is lower than the target frequency (causing a time count loss),

an appropriate time count gain ranges from +3.05ppm to +189.2ppm with the settings of "1, 1, 1, 1, 1, 1, 1"

to "1, 0, 0, 0, 0, 1, 0" written to the F

, F

, and F

bits in the oscillation adjustment register,

thus allowing correction of a time count loss of up to 189.2ppm.

2.4-2 When Oscillation Frequency is Equal to Target Frequency (There is Neither a Time Count Gain nor

a Time Count Loss)

Writing the oscillation adjustment value setting of "0", "+1", "64", or "63" to the oscillation adjustment register

disables the oscillation adjustment circuit.

2.4-3 When Oscillation Frequency is Lower than Target Frequency (There is a Time Count Loss)

Oscillation adjustment value*

(Oscillation frequency Target frequency)

Oscillation frequency

3.051

= (Oscillation frequency Target frequency)

Oscillation adjustment value calculations are exemplified below.

(1) For an oscillation frequency of 32768.85Hz and a target frequency of 32768.05Hz:

Oscillation adjustment value = (32768.85 32768.05 + 0.1) / (32768.85

3.051

) = (32768.85 32768.05)

10 + 1

= 9.001 = 9

In this instance, write the settings of "0, 0, 0, 1, 0, 0, 1" to the F

, F

, and F

bits in the oscillation

adjustment register. Thus, an appropriate oscillation adjustment value in the presence of any time count gain

represents a distance from 01h.

(2) For an oscillation frequency of 32763.95Hz and a target frequency of 32768.05Hz:

Oscillation adjustment value = (32763.95 32768.05) / (32763.95

3.051

) = (32763.95 32768.05)

= 41.015 = 41

To represent an oscillation adjustment value of 41 in 7-bit coded decimal notation, subtract 41(29h) from

128(80h) to obtain 57h. In this instance, write the settings of "1, 0, 1, 0, 1, 1, 1" in the F

, F

, and F

bits in the oscillation adjustment register. Thus, an appropriate oscillation adjustment value in the presence of

any time count loss represents a distance from 80h.

Oscillation adjustment involves an adjustment differential of approximately ±1.5ppm from the target frequency

at normal temperature.

. .

5C338A

3. Oscillation Halt Sensing and Supply Voltage Monitoring

The oscillation halt sensing circuit is configured to record a halt in the oscillation of 32.768-kHz clock pulses. The

supply voltage monitoring circuit is configured to record a drop in supply voltage below a threshold voltage of 2.1 or

1.6 volts. For these functions, the real-time clock has two flag bits (i.e. the XSTP bit for the former and the VDET bit

for the latter) in which 1 is set once and this setting is maintained until 0 is written.

When the XSTP bit is set to 1 for the oscillation halt sensing circuit, the VDET bit is reset to 0 for the supply voltage

monitoring circuit. The relationship between the XSTP and VDET bits is shown in the table below.

The Oscillation halt sensing circuit operates only when the CE pin is Low. The sensing result is maintained after

the CE pin changes from "L" to "H" (See "6.4 Connection of CE Pin").

XSTP

VDET

Conditions of supply voltage and oscillation

No drop in supply voltage below threshold voltage and no halt in oscillation

Drop in supply voltage below threshold voltage and no halt in oscillation

Halt on oscillation

Supply voltage

Threshold voltage (2.1 or 1.6 volts)

Setting XSTP and
VDET bits to 0

Internal initialization
period
(1 to 2 seconds)

Setting VDET bit to 0

Oscillation by 32.768-kHz clock pulses

Normal voltage detector

Supply voltage monitoring (VDET)

Oscillation halt sensing (XSTP)

When the XSTP bit is set to 1 in the control register 2, the (0), F

to F

, WALE, DALE, 12/24, CLEN2, TEST, CT2,

CT1, CT0, VDSL, VDET, SCRATCH, CLEN1, CTFG, WAFG, and DAFG bits are reset to 0 in the oscillation

adjustment register, the control register 1, and the control register 2. When the CE pin is "H" at power on from 0

volts, the XSTP bit is undefined, and the above bits are undefined (See "6.4 Connection of CE Pin"). The XSTP bit is

also set to 1 at power-on from 0 volts. Note that the XSTP bit may be locked to 0 and the internal register broken

upon instantaneous power-down.

5C338A

< Supply Voltage Sensing Circuit >

The supply voltage monitoring circuit is configured to conduct a sampling operation during an interval of 7.8ms per

second to check for a drop in supply voltage below a threshold voltage of 2.1 or 1.6 volts for the VDSL bit setting of 0

(the default setting) or 1, respectively, in the control register 2, thus minimizing supply current requirements as

illustrated in the timing chart below. This circuit suspends a sampling operation once the VDET bit is set to 1 in the

control register 2.

7.8ms

Threshold voltage
of 2.1 or 1.6 volts

Setting 0 to XSTP
and VDET bits

Setting VDET bit to 0

VDD

XSTP

Sampling operation by supply voltage

monitoring circuit

VDET

(D6 at address Fh)

Internal initialization period

(1 or 2 seconds)

Considerations in Using Oscillation Halt Sensing Circuit

Be sure to prevent the oscillation halt sensing circuit from malfunctioning by preventing the following:

1) Instantaneous power-down on the V

2) Condensation on the crystal oscillator

3) On-board noise to the crystal oscillator

4) Applying to individual pins voltage exceeding their respective maximum ratings

In particular, note that the XSTP bit may fail to be set to 1 in the presence of any applied supply voltage as

illustrated below in such events as backup battery installation. Further, give special considerations to prevent

excessive chattering to power supply.

VDD

5C338A

4. Alarm and Periodic Interrupt

The R

5C338A incorporate the alarm circuit and the periodic interrupt circuit that are configured to generate alarm

signals and periodic interrupt signals, respectively, for output from the INTR pin as described below.

1)Alarm Circuit

The alarm interrupt circuit is configured to generate alarm signals for output from the INTR, which is driven low

(enabled) upon the occurrence of a match between current time read by the time counters (the day-of-week, hour,

and minute counters) and alarm time preset by the alarm registers (the Alarm_W registers intended for the day-

of-week, hour, and minute digit settings and the Alarm_D registers intended for the hour and minute digit set-

tings).

2)Periodic Interrupt Circuit

The periodic interrupt circuit is configured to generate either clock pulses in the pulse mode or interrupt signals

in the level mode for output from the INTR pin depending on the CT

, CT

, and CT

bit settings in the control reg-

ister 1.

The above two types of interrupt signals are monitored by the flag bits (i.e. the WAFG, DAFG, and CTFG bits in the

control register 2) and enabled or disabled by the enable bits (i.e. the WALE, DALE, CT

, CT

, and CT

bits in the

control register 1) as listed in the table below.

Flag bits

Enable bits

Alarm signals

WAFG bit

WALE bit

(under control of Alarm_W registers)

(D1 at Address Fh)

(D7 at Address Eh)

Alarm signals

DAFG bit

DALE bit

(under control of Alarm_D registers)

(D0 at Address Fh)

(D6 at Address Eh)

Periodic interrupt signals

CTFG bit

, CT

, and CT

bits (D2 to D0 at Address Eh)

(D2 at Address Fh)

(these bit settings of 0 disable the periodic interrupt circuit)

· At power-on, when the WALE, DALE, CT

, CT

, and CT

bits are set to 0 in the control register 1, the INTR pin is

driven high (disabled).

· When two or more types of interrupt signals are output simultaneously from the INTR pin, the output from the

INTR pin becomes an OR waveform of their negative logic.

Alarm_W

Alarm_D

INTR

In this event, which type of interrupt signal is output from the INTR pin can be confirmed by reading the

WAFG, DAFG, and CTFG bit settings in the control register 2.

Example: Combined Output of Alarm Interrupt Signals from the INTR pin Under Control of Alarm_D and

Alarm_W Registers

5C338A

4.1 Alarm Interrupt

The alarm circuit is controlled by the enable bits (i.e. the WALE and DALE bits in the control register 1) and the

flag bits (i.e. the WAFG and DAFG bits in the control register 2). The enable bits can be used to enable this circuit

when set to 1 and to disable it when set to 0. When intended for reading, the flag bits can be used to monitor alarm

interrupt signals. When intended for writing, the flag bits will cause no event when set to 1 and will drive high (dis-

able) the alarm circuit when set to 0.

The enable bits will not be affected even when the flag bits are set to 0. In this event, therefore, the alarm circuit will

continue to function until it is driven low (enabled) upon the next occurrence of a match between current time and

preset alarm time.

The alarm function can be set by presetting desired alarm time in the alarm registers (the Alarm_W registers for the

day-of-week digit settings and both the Alarm_W registers and the Alarm_D registers for the hour and minute digit

settings) with the WALE and DALE bits once set to 0 and then to 1 in the control register 1. Note that the WALE

and DALE bits should be once set to 0 in order to disable the alarm circuit upon the coincidental occurrence of a

match between current time and preset alarm time in the process of setting the alarm function.

Interval (1 minute) during which
a match between current time
and preset alarm time occurs

INTR pin

Setting WALE
and DALE
bit to 1

Match between
current time and
preset alarm time
in the day-of-week
and hour settings

Setting WALE
and DALE
bit to 0

Setting WALE
and DALE
bit to 1

Match between
current time and
preset alarm time
in the day-of-week
and hour settings

Setting WAFG
and DAFG
bit to 0

Setting WALE
and DALE
bit to 1

Setting WALE
and DALE
bit to 0

MAX.61.1

5C338A

4.2 Periodic Interrupt

Setting of the periodic selection bits (CT

to CT

) enables periodic interrupt to the CPU. There are two waveform

modes: pulse mode and level mode. In the pulse mode, the output has a waveform duty cycle of around 50%. In the

level mode, the output is cyclically driven low and, when the CTFG bit is set to 0, the output is set to high (OFF).

Waveform Mode, Cycle and Falling Timing

1) Pulse Mode : 2-Hz and 1-Hz clock pulses are output in synchronization with the increment of the second counter

as illustrated in the timing chart on the next page.

2) Level Mode : periodic interrupt signals are output with selectable interrupt cycle settings of 1 second, 1 minute, 1

hour, and 1 month. The increment of the second counter is synchronized with the falling edge of

periodic interrupt signals. For example, periodic interrupt signals with an interrupt cycle setting of

1 second are output in synchronization with the increment of the second counter as illustrated in

the timing chart on the next page.

3) When the oscillation adjustment circuit is used, the interrupt cycle will fluctuate once per 20 seconds as follows:

Pulse Mode : the "L" period of output pulses will increment or decrement by a maximum of ±3.784ms.

For example, 1-Hz clock pulses will have a duty cycle of 50 ±0.3784%.

Level Mode : a periodic interrupt cycle of 1 second will increment or decrement by a maximum of ±3.784ms.

Description

Waveform mode

Cycle and falling timing

Off ("H")

Fixed at low ("L")

Pulse Mode

2Hz (Duty cycle of 50%)

Pulse Mode

1Hz (Duty cycle of 50%)

Level Mode

Once per 1 second (Synchronized with second counter increment)

Level Mode

Once per minute (at 00 seconds of every minute)

Level Mode

Once per hour (at 00 minutes and 00 seconds of every hour)

Level Mode

Once per month (at 00 hours, 00 minutes, and 00 seconds of first day of every month)

(Default setting)

5C338A

Approx. 92

CTFG bit

INTR pin

(Increment of second counter)

Rewriting of the second counter

Relation Between the Mode Waveform and the CTFG Bit

· Pulse mode

) In the pulse mode, the increment of the second counter is delayed by approximately 92 µs from the falling edge of clock pulses. Consequently, time

readings immediately after the falling edge of clock pulses may appear to lag behind the time counts of the real-time clocks by approximately 1 second.

Rewriting the second counter will reset the other time counters of less than 1 second, driving the INTR pin low.

Setting CTFG bit to 0

(Increment of

second counter)

Setting CTFG bit to 0

CTFG bit

INTR pin

(Increment of

second counter)

(Increment of

second counter)

5. 32-kHz Clock Output

32.768-kHz clock pulses are output from the 32KOUT pin when either the CLEN1 bit in the control register 2 or the

CLEN2 bit in the control register 1 is set to 0 when the CLKC pin is set to high. If the conditions described above

are not satisfied, the output is set to high.

CLEN1

CLEN2

CLKC pin output

32KOUT pin output

(D3 at Address Fh)

(D4 at Address Eh)

(CMOS output)

"L"

0 (Default)

Clock pulses

0 (Default)

The 32KOUT pin output is synchronized with the CLEN1, CLEN2 bit, and CLKC pin settings as illustrated in the tim-

ing chart below.

MAX. 76.3

32KOUT pin output

CLKC pin or

CLEN1 or CLEN2 bit setting

· Level mode

5C338A

6.2 Connection of INTR Pin

The INTR pin follows the N-channel open drain output logic and contains no protective diode on the power supply

side. As such, it can be connected to a pull-up resistor of up to 5.5 volts regardless of supply voltage.

6.3 Connection of 32KOUT Pin

As the 32KOUT pin is CMOS output, the voltages of the R

5C338A and any devices to be connected should be the

same. When the device is powered down, the 32KOUT output should be disabled.

When the CLKC pin is connected to the system power supply through the pull-up resistor, the pull-up resistor

should be 0

to 10k

, and the 32KOUT pin should be connect to the host through the resistor (approx. 10k

System power supply

5C338A

OSCIN

OSCOUT

VDD

VSS

INTR

Backup power supply

32.768kHz

System power supply

OSCIN

OSCOUT

VDD

VSS

32KOUT

CLKC

Backup power supply

Voltage detector IC

5C338A

32.768kHz

System power supply

OSCIN

OSCOUT

VDD

VSS

32KOUT

CLKC

Backup power
supply

5C338A

32.768kHz

Host

0 to 10k

Approx.10k

1) Depending on whether the INTR pin is to be used during bat-

tery backup, it should be connected to a pull-up resistor at the

following different positions:

1) Position A in the left diagram when it is not to be used during

battery backup.

2) Position B in the left diagram when it is to be used during

battery backup.

1) RN5VL

××

C by RICOH.

5C338A

6.4 Connection of CE Pin

Observe the following precautions when you connect the CE pin.

1) The CE pin is configured to enable the oscillation halt sensing circuit only when driven low. As such, it should be

driven low or open at power-on from 0 volts.

2) The CE pin should also be driven low or open immediately upon the host going down (see "1.5 Considerations in

Reading and Writing Time Count Data").

3) The reading function should be disrupted when the CE signal goes to "low" during read cycle. While, the upper 4

bits of the data might be written to the inner shift register when the CE signal goes to "low" during write cycle.

(Because the writing function is executed 4 bits by 4 bits.) In either case, after the CE signal returns to "High",

no trouble will occur in the next read or write cycle.

I/O

CONTROL

SCLK

SIO

Lower limit operating voltage
for the CPU

Backup voltage

0.2

MIN. 0

5C338A

X'tal : 32.768kHz

=30k

TYP.)

=6pF to 8pF)

Topt : 25°C

Output pins : Open

Frequency

counter

5C338A

32.768kHz

OSCIN

OSCOUT

VDD

32KOUT

7.1 Timekeeping Current vs. Supply Voltage

(with no 32-kHz clock output)

Supply Voltage V

(V)

0.2

0.4

0.6

0.8

i
m

i
n

r
r
e

t

I

(

)

(CE=Open, Output=Open, Topt=25°C)

Supply Voltage V

(V)

0.5

1.5

2.5

i
m

i
n

r
r
e

t

I

(

)

(CE=Open, Output=Open, Topt=25°C)

7.3 CPU Access Current vs. SCLK Clock Frequency

SCLK Clock Frequency (kHz)

500

1000

1500

2000

r
r
e

t

I

(

)

(Output=Open, Topt=25°C)

=5V

=3V

Operating Temperature Topt(°C)

60 40

0.5

1.5

i
m

i
n

r
r
e

t

I

(

)

(CE=Open, Output=Open, Topt=25°C)

7. Typical Characteristics

Test Circuit

7.2 Timekeeping Current vs. Supply Voltage

(with 32-kHz clock output)

7.4 Timekeeping Current vs. Operating Temperature

(with no 32-kHz clock output)

5C338A

7.5 Oscillation Frequency Deviation vs. External C

External C

(pF)

i
l
l
a

t
i
o

r
e

i
a

t
i
o

(
p

)

=3V, Topt=25°C,

External C

=0pF as standard)

7.6 Oscillation Frequency Deviation vs. Supply Voltage

Supply Voltage V

(V)

i
l
l
a

t
i
o

r
e

i
a

t
i
o

(
p

)

(Topt=25°C, V

=3V as standard)

7.7 Oscillation Frequency Deviation vs.

Operating Temperature

Operating Temperature Topt(°C)

60 40 20

140

100

120

80 100

i
l
l
a

t
i
o

r
e

i
a

t
i
o

(
p

)

=3V, External C

=0pF,

Topt=25°C as standard)

Supply Voltage V

(V)

100

200

300

500

400

i
l
l
a

t
i
o

t
a

r
t

T

i
m

(
m

)

(Topt=25°C)

7.9 V

vs. I

(INTR Pin)

(V)

0.2

0.4

0.6

0.8

1.0

(
m

)

(Topt=25°C)

=3V

=5V

7.10 Input Current to CLKC Pin vs. Supply Voltage

Supply Voltage V

(V)

0.2

0.4

0.6

0.8

(

)

(Topt=25°C)

7.8 Oscillation Start Time vs. Supply Voltage

5C338A

8. Typical Software-based Operations

8.1 Initialization at Power-on

Start

XSTP=1?

Power-on

YES

Warning of Backup Battery
Run-down

VDET=0?

Set Oscillation Adjustment Register
and Control Registers 1 and 2, etc.

8.2 Writing of Time and Calendar Data

Wait for 31

Write to Time Counter
and Calendar Counter

1) After power-on from 0 volts, the start of oscillation and the process of internal initialization require a time span on the order of 1 to 2 seconds, so that

access should be done after the lapse of this time span or more.

2) The XSTP bit setting of 0 in the control register 1 indicates power-on from backup battery and not from 0 volt. The XSTP bit may fail to be set to 1 in the

presence of any excessive chattering in power supply in such events as installing backup battery. Should there be any possibility of this failure occurring,

it is recommended to initialize the R

5C338A regardless of the current XSTP bit setting. For further details, see "3. Oscillation Halt Sensing and Supply

Voltage Monitoring".

3) This step is not required when the supply voltage monitoring circuit is not used.

4) This step involves ordinary initialization including the oscillation adjustment register and interrupt cycle settings.

1) This step of waiting is detailed in "1.5 Considerations in Reading

and Writing Time Data".

2) Any writing to the second counter will reset divider units lower than

the second digits.

5C338A

8.3 Reading Time and Calendar Data

8.3-1 Ordinary Process of Reading Time and Calendar Data

Wait for 31

Read from Time Counter
and Calendar Counter

8.3-2 Basic Process of Reading Time and Calendar Data Synchronized with Periodic Interrupt

CTFG=1?

Other Interrupt
Processes

Generate Interrupt in CPU

Write "

,1,

,0,1,1"

to Control Register 2

Set Periodic Interrupt
Cycle Selection Bits

YES

Read from Time Counter
and Calendar Counter

1) This step of waiting is detailed in "1.5 Considerations in Reading and

Writing Time Data".

1) This step is intended to select the level mode as a waveform mode for the

periodic interrupt function.

2) If this step is completed within 1 second, the step of waiting described in

"8.3-1 Ordinary Process of Reading Time and Calendar Data" above need

not be conducted. This step is detailed in "1.5 Considerations in Reading

and Writing Time Data".

3) This step is intended to set the CTFG bit to 0 in the control register 2 to

cancel an interrupt to the CPU.

5C338A

8.3-3 Applied Process of Reading Time and Calendar Data Synchronized with Periodic Interrupt Function

Time data need not be read from all the time counters when used for such ordinary purposes as time count

indication. This applied process can be used to read time and calendar data with substantial reductions in the load

involved in such reading.

CTFG=1?

Generate Interrupt to CPU

Write "

,0,1,0,0"

to control Register 1
Write "

,1,

,0,1,1"

to Control Register 2

YES

Second Digit=00?

YES

Use Previous Minute,
Hour, Day-of-week,
and Day-of-month Data

Read Minute, Hour, Day-of-week,
and Day-of-month Counters

Other Interrupt
Processes

Write "

,1,

,0,1,1"

to Control Register 2

For Time Indication in "Day-of-month, Day-of-week, Hour,

Minute, and Second" Format:

1) This step is intended to select the level mode as a waveform mode for the periodic interrupt function.

2) If this step is completed within 1 second, the step of waiting described in "8.3-1 Ordinary Process of Reading Time and Calendar Data" above need not be

conducted. This step is detailed in "1.5 Considerations in Reading and Writing Time Data".

3) This step is intended to read time data from all the time counters only in the first session of reading time data after writing time data.

4) This step is intended to set the CTFG bit to 0 in the control register 2 to cancel an interrupt to the CPU.

5C338A

YES

Periodic Interrupt Process

CTFG=1?

Other Interrupt
Processes

Generate Interrupt to CPU

Write "

,1,

,0,1,1"

to Control Register 2

Set Periodic Interrupt
Cycle Selection Bits

WAFG or DAFG=1?

Generate Interrupt to CPU

WALE or DALE=1

YES

Conduct Alarm Interrupt

WALE or DALE=0

Set Alarm Minute, Hour,
and Day-of-week Registers

Other Interrupt
Processes

Write "

,1,

,1,0,1"

to Control Register 2

8.4-2 Alarm Interrupt

8.4 Interrupt Process

8.4-1 Periodic Interrupt

1) This step is intended to select the level mode as a waveform mode for the

periodic interrupt function.

2) This step is intended to set the CTFG bit to 0 in the control register 2 to

cancel an interrupt to the CPU.

1) This step is intended to once disable the alarm interrupt circuit by setting

the WALE and DALE bits to 0 in anticipation of the coincidental occurrence

of a match between current time and preset alarm time in the process of

setting the alarm interrupt function.

2) This step is intended to enable the alarm interrupt function after completion

of all alarm interrupt settings.

3) This step is intended to once cancel the alarm interrupt function by writing

the settings of "

,1,

,1,0,1" and "

,1,

,1,1,0" to the Alarm_W

registers and the Alarm_D registers, respectively.

5C338A

0.3

2.7MAX.

4.0

0.1

2.0

0.05

8.0

0.1

.
7

.
1

.
5

.
0

.
9

6.7

.
0

.
3

User Direction of Feed.

ø1.5

+0.1
0

ø1.5

+0.1
0

2.0MAX.

4.4

8.0

0.1

.
2

.
7

.
1

.
5

.
0

.
3

0.3

4.0

0.1

2.0

0.05

User Direction of Feed.

TAPING SPECIFICATIONS

(Unit : mm)

The RV5C338A has one designated taping direction. The product designation for the taping components is

"RV5C338A-E2".

· RV5C338A (10-pin SSOP-10G)

The RS5C338A has one designated taping direction. The product designation for the taping components is

"RS5C338A-E2".

· RS5C338A (10-pin SSOP)

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: RV5C338A-E2

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: RV5C338A-E2