1996 Microchip Technology Inc.

Preliminary

DS21159B-page 1

FEATURES

· SPI modes 0,0 and 1,1
· 3.0 MHz Clock Rate
· Single 5V Supply
· Low Power CMOS Technology

- Max Write Current: 5 mA
- Read Current: 1.0 mA at 5.5V, 3MHz
- Standby Current: 1

A typical

· 4096 x 8 Organization
· 32 Byte Page
· Sequential Read
· Self-timed ERASE and WRITE Cycles
· Block Write Protection

- Protect none, 1/4, 1/2, or all of Array

· Built-in Write Protection

- Power On/Off Data Protection Circuitry
- Write Enable Latch
- Write Protect Pin

· High Reliability

- Endurance: 1M cycles (guaranteed)
- Data Retention: >200 years
- ESD protection: >4000V

· 8-pin PDIP/SOIC, 14-pin TSSOP
· Temperature ranges supported

DESCRIPTION

The Microchip Technology Inc. 25C320 is a 32K-bit
serial Electrically Erasable PROM (EEPROM). The
memory is accessed via a simple Serial Peripheral
Interface (SPI) compatible serial bus. The bus signals
required are a clock input (SCK) plus separate data in
(SI) and data out (SO) lines. Access to the device is
controlled through a chip select (CS) input, allowing any
number of devices to share the same bus.

There are two other inputs that provide the end user
with additional flexibility. Communication to the device
can be paused via the hold pin (HOLD). While the
device is paused, transitions on its inputs will be
ignored, with the exception of chip select, allowing the
host to service higher priority interrupts. Also write
operations to the Status Register can be disabled via
the write protect pin (WP).

- Commercial (C):

C to

+70

- Industrial (I):

-40

C to

+85

- Automotive (E):

-40

C to +125

PACKAGE TYPES

BLOCK DIAGRAM

DIP/SOIC

25C320

HOLD

SCK

25C32

14
13
12
11
10

9
8

HOLD
NC
NC
NC
SCK
SI

1
2
3
4
5
6
7

CS
SO
NC
NC
NC
WP
V

TSSOP

SCK

HOLD

Status

I/O Control

Memory

Control

Logic

Dec

HV Generator

EEPROM

Array

Page Latches

Y Decoder

Sense Amp.
R/W Control

Logic

Vcc
Vss

25C320

32K 5.0V SPI

Bus Serial EEPROM

SPI is a trademark of Motorola.

This document was created with FrameMaker 4 0 4

25C320

DS21159B-page 2

Preliminary

1996 Microchip Technology Inc.

1.0

ELECTRICAL
CHARACTERISTICS

1.1

Maximum Ratings*

........................................................................ 7.0V

All inputs and outputs w.r.t. V

....... -0.6V to V

+1.0V

Storage temperature ............................ -65

C to 150

Ambient temperature under bias .......... -65

C to 125

Soldering temperature of leads
(10 seconds) .................................................... +300

ESD protection on all pins..................................... 4 kV

*Notice:

Stresses above those listed under `Maximum ratings'

may cause permanent damage to the device. This is a stress rat-
ing only and functional operation of the device at those or any
other conditions above those indicated in the operational listings
of this specification is not implied. Exposure to maximum rating
conditions for extended period of time may affect device reliability

TABLE 1-1:

PIN FUNCTION TABLE

Name

Function

Chip Select Input

Serial Data Output

Serial Data Input

SCK

Serial Clock Input

Write Protect Pin

Ground

Supply Voltage

HOLD

Hold Input

No Connect

FIGURE 1-1: AC TEST CIRCUIT

1.2

AC Test Conditions

AC Waveform:

= 0.2V

= Vcc - 0.2V

(Note 1)

= 4.0V

(Note 2)

Timing Measurement Reference Level

Input

0.5 V

Output

0.5 V

Note 1: For V

4.0V

2: For V

> 4.0V

Vcc

100 pF

1.8 K

2.25 K

TABLE 1-2:

DC CHARACTERISTICS

Applicable over recommended operating ranges shown below unless otherwise noted:
V

= 4.5V to 5.5V

Commercial (C):

Tamb = 0

C to +70°C

Industrial (I):

Tamb =-40°C to +85°C

Automotive (E):

Tamb = -40

C to +125

Parameter

Symbol

Min

Max

Units

Test Conditions

High level input voltage

2.0

Low level input voltage

-0.3

0.8

Low level output voltage

0.4

=2.1 mA

High level output voltage

-0.5

=-400

Input leakage current

-10

CS=V

, V

=GND to V

Output leakage current

-10

CS=V

, V

OUT

=GND to V

Internal Capacitance
(all inputs and outputs)

INT

Tamb=25

C, F

CLK

=1.0 MHz,

=5.5V (Note)

Operating Current

CC write

----

=5.5V; SO=Open

read

=5.5V; SO=Open, F

CLK

=3.0 MHz

Standby Current

CCS

CS=V

=5.5V; V

=Gnd or V

Note:

This parameter is periodically sampled and not 100% tested.

25C320

DS21159B-page 4

Preliminary

1996 Microchip Technology Inc.

TABLE 1-3:

AC CHARACTERISTICS

Applicable over recommended operating ranges shown below unless otherwise noted:
V

= 4.5V to 5.5V

Commercial (C):

Tamb = 0

C to +70

Industrial (I):

Tamb = +40

C to +85C

Automotive (E):

Tamb = -40

C to +125

Symbol

Parameter

Min

Max

Units

Test Conditions

SCK

Clock Frequency

MHz

CSS

CS Setup Time

100

CSH

CS Hold Time

100

CSD

CS Disable Time

250

Data Setup Time

Data Hold Time

CLK Rise Time

(Note 1)

CLK Fall Time

(Note 1)

Clock High Time

150

Clock Low Time

150

CLD

Clock Delay Time

Output Valid from
Clock Low

150

Output Hold Time

DIS

Output Disable Time

200

(Note 1)

HOLD Setup Time

100

HOLD Hold Time

100

HOLD Low to Output High-Z

100

(Note 1)

HOLD High to Output Valid

100

(Note 1)

Internal Write Cycle Time

(Note 2)

Endurance

E/W Cycles 25

C, Vcc = 5.0V, Block Mode

(Note 3)

Note 1: This parameter is periodically sampled and not 100% tested.

2: t

begins on the rising edge of CS after a valid write sequence and ends when the internal self-timed write

cycle is complete.

3: This parameter is not tested but guaranteed by characterization. For endurance estimates in a specific appli-

cation, please consult the Total Endurance Model which can be obtained on our BBS or website.

1996 Microchip Technology Inc.

Preliminary

DS21159B-page 5

25C320

2.0

PRINCIPLES OF OPERATION

The 25C320 is a 4096-byte EEPROM designed to
interface directly with the serial peripheral interface (SPI)
port of many of today's popular microcontroller families,
including Microchip's midrange PIC16CXX microcontrol-
lers. It may also interface with microcontrollers that do
not have a built-in SPI port by using discrete I/O lines
programmed properly with software.

The 25C320 contains an 8-bit instruction register. The
part is accessed via the SI pin, with data being clocked
in on the rising edge of SCK. The CS pin must be low
and the HOLD pin must be high for the entire operation.
If the WPEN bit in the status register is set, the WP pin
must be held high to allow writing to the nonvolatile bits
in the status register.

Table 2-1 contains a list of the possible instruction bytes
and format for device operation. All instructions,
addresses and data are transferred MSB first, LSB last.

Data is sampled on the first rising edge of SCK after CS
goes low. If the clock line is shared with other peripheral
devices on the SPI bus, the user can assert the HOLD
input and place the 25C320 in `HOLD' mode. After
releasing the HOLD pin, operation will resume from the
point when the HOLD was asserted.

2.1

Write Enable (WREN) and Write
Disable (WRDI)

The 25C320 contains a write enable latch. This latch
must be set before any write operation will be
completed internally. The WREN instruction will set the
latch, and the WRDI will reset the latch. The following is
a list of conditions under which the write enable latch
will be reset:

· Power-up
· WRDI instruction successfully executed
· WRSR instruction successfully executed
· WRITE instruction successfully executed

2.2

Read Status Register (RDSR)

The RDSR instruction provides access to the status
register. The status register may be read at any time,
even during a write cycle. The status register is format-
ted as follows:

The Write-In-Process (WIP) bit indicates whether the
25C320 is busy with a write operation. When set to a `1'
a write is in progress, when set to a `0' no write is in
progress. This bit is read only.

WPEN

BP1

BP0

WEL

WIP

The Write Enable Latch (WEL) bit indicates the status
of the write enable latch. When set to a `1' the latch
allows writes to the array and status register, when set
to a `0' the latch prohibits writes to the array and status
register. The state of this bit can always be updated via
the WREN or WRDI commands regardless of the state
of write protection on the status register. This bit is read
only.

The Block Protection (BP0 and BP1) bits indicate
which blocks are currently write protected. These bits
are set by the user issuing the WRSR instruction.
These bits are non-volatile.

The Write Protect Enable (WPEN) bit is a nonvolatile
bit that is available as an enable bit for the WP pin. The
Write Protect (WP) pin and the Write Protect Enable
(WPEN) bit in the status register control the
programmable hardware write protect feature.
Hardware write protection is enabled when the WP pin
is low and the WPEN bit is high. Hardware write
protection is disabled when either the WP pin is high or
the WPEN bit is low. When the chip is hardware write
protected, only writes to nonvolatile bits in the status
register are disabled. See Table 2-2 for matrix of
functionality on the WPEN bit and Figure 2-1 for a
flowchart of Table 2-2.

See Figure 3-5 for RDSR timing sequence.

TABLE 2-1:

INSTRUCTION SET

Instruction

Name

Instruction

Format

Description

WREN

0000 0110

Set the write enable latch

(enable write operations)

WRDI

0000 0100

Reset the write enable

latch (disable write opera-
tions)

RDSR

0000 0101

Read status register

WRSR

0000 0001

Write status register (write

protect enable and block
write protection bits)

READ

0000 0011

Read data from memory

array beginning at
selected address

WRITE

0000 0010

Write data to Memory

Array beginning at
Selected Address

1996 Microchip Technology Inc.

Preliminary

DS21159B-page 7

25C320

2.3

Write Status Register (WRSR)

The WRSR instruction allows the user to select one of
four protection options for the array by writing to the
appropriate bits in the status register. The array is
divided up into four segments. The user has the ability
to write protect none, one, two, or all four of the seg-
ments of the array. The partitioning is controlled as illus-
trated in Table 2-3.

See Figure 3-6 for WRSR timing sequence.

TABLE 2-3:

ARRAY PROTECTION

3.0

DEVICE OPERATION

3.1

Clock and Data Timing

Data input on the SI pin is latched on the rising edge of
SCK. Data is output on the SO pin after the falling edge
of SCK.

3.2

Read Sequence

The part is selected by pulling CS low. The 8-bit read
instruction is transmitted to the 25C320 followed by the
16-bit address, with the four MSBs of the address being
don't care bits. After the correct read instruction and
address are sent, the data stored in the memory at the
selected address is shifted out on the SO pin. The data
stored in the memory at the next address can be read
sequentially by continuing to provide clock pulses. The
internal address pointer is automatically incremented to
the next higher address after each byte of data is
shifted out. When the highest address is reached
(0FFFh) the address counter rolls over to address
0000h allowing the read cycle to be continued indefi-
nitely. The read operation is terminated by setting CS
high (Figure 3-1).

3.3

Write Sequence

Prior to any attempt to write data to the 25C320, the
write enable latch must be set by issuing the WREN
instruction (Figure 3-2). This is done by setting CS low
and then clocking the proper instruction into the
25C320. After all eight bits of the instruction are trans-
mitted, the CS must be brought high to set the write
enable latch. If the write operation is initiated
immediately after the WREN instruction without CS
being brought high, the data will not be written to the
array because the write enable latch will not have been
properly set.

BP1

BP0

Array Addresses

Write Protected

none

upper 1/4

0C00h - 0FFFh

upper 1/2

0800h - 0FFFh

all

0000h - 0FFFh

Once the write enable latch is set, the user may pro-
ceed by setting the CS low, issuing a write instruction,
followed by the 16-bit address, with the four MSBs of
the address being don't care bits, and then the data to
be written. Up to 32 bytes of data can be sent to the
25C320 before a write cycle is necessary. The only
restriction is that all of the bytes must reside in the
same page. A page address begins with XXXX XXXX
XXX0 0000 and ends with XXXX XXXX XXX1 1111. If
the internal address counter reaches XXXX XXXX
XXX1 1111 and the clock continues, the counter will roll
back to the first address of the page and overwrite any
data in the page that may have been written.

For the data to be actually written to the array, the CS
must be brought high after the least significant bit (D0)
of the n

data byte has been clocked in. If CS is brought

high at any other time, the write operation will not be
completed. Refer to Figure 3-3 and Figure 3-4 for more
detailed illustrations on the byte write sequence and the
page write sequence respectively.

While the write is in progress, the status register may
be read to check the status of the WPEN, WIP, WEL,
BP1, and BP0 bits. A read attempt of a memory array
location will not be possible during a write cycle. When
a write cycle is completed, the write enable latch is
reset.

3.4

Data Protection

The following protection has been implemented to
prevent inadvertent writes to the array:

· The write enable latch is reset on power-up.
· A write enable instruction must be issued to set

the write enable latch.

· After a successful byte write, page write, or status

· CS must be set high after the proper number of

clock cycles to start an internal write cycle.

· Access to the array during an internal write cycle

is ignored and programming is continued.

3.5

Power On State

The 25C320 powers on in the following state:

· The device is in low power standby mode (CS=1).
· The write enable latch is reset.
· SO is in high impedance state.
· A low level on CS is required to enter active state.

1996 Microchip Technology Inc.

Preliminary

DS21159B-page 9

25C320

FIGURE 3-4: PAGE WRITE SEQUENCE

FIGURE 3-5: READ STATUS REGISTER SEQUENCE

FIGURE 3-6: WRITE STATUS REGISTER SEQUENCE

9 10 11

21 22 23 24 25 26 27 28 29 30 31

15 14 13 12

instruction

16-bit address

data byte 1

SCK

41 42 43

46 47

data byte n (32 max)

SCK

34 35 36 37 38 39

data byte 3

data byte 2

44 45

10 11

12 13 14 15

instruction

data from status register

high impedance

SCK

10 11

12 13 14 15

instruction

data to status register

high impedance

SCK

25C320

DS21159B-page 10

Preliminary

1996 Microchip Technology Inc.

4.0

PIN DESCRIPTIONS

4.1

Chip Select (CS)

A low level on this pin selects the device. A high level
deselects the device and forces it into standby mode.
However, a programming cycle which is already in
progress will be completed, regardless of the CS input
signal. If CS is brought high during a program cycle, the
device will go into standby mode as soon as the pro-
gramming cycle is complete. As soon as the device is
deselected, SO goes to the high impedance state,
allowing multiple parts to share the same SPI bus. A
low to high transition on CS after a valid write sequence
is what initiates an internal write cycle. After power-up,
a low level on CS is required prior to any sequence
being initiated.

4.2

Serial Input (SI)

The SI pin is used to transfer data into the device. It
receives instructions, addresses, and data to be written
to the memory. Input is latched on the rising edge of the
serial clock.

It is possible for the SI pin and the SO pin to be tied
together. With SI and SO tied together, two way
communication of data can occur using only one
microcontroller I/O line.

4.3

Serial Output (SO)

The SO pin is used to transfer data out of the 25C320.
During a read cycle, data is shifted out on this pin after
the falling edge of the serial clock.

It is possible for the SI pin and the SO pin to be tied
together. With SI and SO tied together, two-way
communication of data can occur using only one
microcontroller I/O line.

4.4

Serial Clock (SCK)

The SCK is used to synchronize the communication
between a master and the 25C320. Instructions,
addresses, or data present on the SI pin are latched on
the rising edge of the clock input, while data on the SO
pin is updated after the falling edge of the clock input.

4.5

Write Protect (WP)

This pin is used in conjunction with the WPEN bit in the
status register to prohibit writes to the non-volatile bits
in the status register. When WP is low and WPEN is
high, writing to the non-volatile bits in the status register
is disabled. All other operations function normally.
When WP is high, all functions, including writes to the
non-volatile bits in the status register operate normally.
If the WPEN bit is set WP going low during a status reg-
ister write sequence will disable writing to the status
register. If an internal write cycle has already begun,
WP going low will have no effect on the write.

The WP pin function is blocked when the WPEN bit in
the status register is low. This allows the user to install
the 25C320 in a system with the WP pin grounded and
still be able to write to the status register. The WP pin
functions will be enabled when the WPEN bit is
set high.

4.6

Hold (HOLD)

The HOLD pin is used to suspend transmission to the
25C320 while in the middle of a serial sequence without
having to re-transmit the entire sequence over at a later
time. It should be held high any time this function is not
being used. Once the device is selected and a serial
sequence is underway, the HOLD pin may be pulled low
to pause further serial communication without resetting
the serial sequence. The HOLD pin must be brought
low while SCK is low, otherwise the HOLD function will
not be evoked until the next SCK high to low transition.
The 25C320 must remain selected during this
sequence. The SI, SCK, and SO pins are in a high
impedance state during the time the part is paused and
transitions on these pins will be ignored. To resume
serial communication, HOLD must be brought high
while the SCK pin is low, otherwise serial communica-
tion will not resume.

25C320

25C320 Product Identification System

To order or to obtain information (e.g., on pricing or delivery), please use the listed part numbers, and refer to the factory or the listed
sales offices.

Package:

PDIP (300 mil Body), 8-lead

SOIC (150 mil Body), 8-lead

TSSOP (4.4 mm Body), 14-lead

Temperature

Blank

C to +70

Range:

-40

C to +85

-40

C to +125

Device:

25C320

32K SPI Bus Serial EEPROM

25C320T

32K SPI Bus Serial EEPROM (Tape and Reel)

25C320

Sales and Support

Products supported by a preliminary Data Sheet may possibly have an errata sheet describing minor operational differences and
recommended workarounds. To determine if an errata sheet exists for a particular device, please contact one of the following:

Your local Microchip sales office (see next page)

The Microchip Corporate Literature Center U.S. FAX: (602) 786-7277
The Microchip's Bulletin Board, via your local CompuServe number (CompuServe membership NOT required).

Please specify which device, revision of silicon and Data Sheet (include Literature #) you are using.
For latest version information and upgrade kits for Microchip Development Tools, please call 1-800-755-2345 or 1-602-786-7302.

2.
3.

1996 Microchip Technology Inc.

Preliminary

DS21159B-page 11

DS21159B-page 12

Preliminary

1996 Microchip Technology Inc.

Information contained in this publication regarding device applications and the like is intended through suggestion only and may be superseded by updates. No repre-
sentation or warranty is given and no liability is assumed by Microchip Technology Incorporated with respect to the accuracy or use of such information, or infringement
of patents or other intellectual property rights arising from such use or otherwise. Use of Microchip's products as critical components in life support systems is not autho-
rized except with express written approval by Microchip. No licenses are conveyed, implicitly or otherwise, under any intellectual property rights. The Microchip logo and
name are registered trademarks of Microchip Technology Inc. All rights reserved. All other trademarks mentioned herein are the property of their respective companies.

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Printed on recycled paper.

Document Outline

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Document Outline

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