Single-Chip USB-to-USB Networking Solution
EZ-Link (AN2720SC)
F
EATURES
Smallest completely integrated solution in the market
32 pin TQFP
Only requires a single crystal and small 16 byte serial EEPROM for full implementation
Meets difficult suspend current of 500 uA for both hosts
2K data buffer for maximum speed transfer
Greater than 5 Mbps data transfer rate
Low power Less than 100 mW power
O
VERVIEW
The Cypress AN2720SC provides a single-chip solution for networking two or more computers
via their USB ports. In a USB system, the PC acts as a host, which initiates all USB traffic. USB
devices act as slaves, which respond to host requests. It is inherently incompatible to connect two
PCs together via a simple USB cable, since a master (host) cannot talk to another master (host).
A master can talk only to one or more slave devices.
The AN2720SC overcomes this "peer-to-peer" incompatibility by providing two USB devices,
one for each PC. Two independent Serial Interface Engines (SIE) exchange data through a 2
kilobyte FIFO. Thus, USB data transmitted by one computer is made available to the other
computer through the AN2720SC. The connection is full duplex data can be transferred in both
directions simultaneously.
AN2720SC Block Diagram System Application
AN2720 Data Sheet Version 1.0
06/07/00
Page 2
EZ-Link (AN2720SC)
A
PPLICATIONS AND
M
ARKETS
The use of the AN2720SC and special network driver software provided by Cypress allows very
simple and efficient networking between PCs. The "plug-and-play" nature of USB makes
connecting two computers (even when powered) very simple. With the AN2720SC, simple
networking can be provided in numerous form factors including:
USB standalone hubs
Computer monitors with USB hubs
Standalone USB cables
Port Replicators
WinCE Machines
Set-Top Boxes
Docking Stations
PC motherboards (particularly for laptops)
Depending on the driver set used, the AN2720SC can perform the following functions:
USB networking
File transfer (including MAC to PC file sharing)
Windows CE synchronization
Printer sharing
Share internet connections (requires proxy or bridging software)
Multi-player gaming
S
YSTEM
D
IAGRAM
Computer
A
U
S
B
U
S
B
AN2720SC
VBUS
D+
D-
GND
VBUS
D+
D-
GND
S
I
E
S
I
E
2
Kilobyte
FIFO
Computer
B
AN2720 Data Sheet Version 1.0
06/07/00
Page 3
EZ-Link (AN2720SC)
C
HIP
D
ETAILS
The AN2720 contains two slave interfaces that transfer data between through a 2-kilobyte FIFO.
It also contains two 5V to 3.3V regulators to supply power to the chip and to the USB pullup
resistor. Figure 2 of this document shows a functional block diagram of the AN2720. The
AN2720 contains:
!
Two 5V to 3.3V regulators, which deliver clean, regulated power to the chip and to
the pullup resistor connected to the USB D+ line. These regulators are powered by the
USB 5V line.
!
Two USB transceivers, one for each computer.
!
Two USB cores, each consisting of a Serial Interface Engine (SIE) and an intelligent
machine that can respond to standard USB requests. These are the same enhanced SIE's
used in Cypress' line of EZ-USB products.
!
A 2-Kilobyte FIFO which is used to buffer multiple packets between computers to
optimize data throughput.
!
Control logic to manage transfer of USB data between the two SIEs.
!
A single-crystal oscillator and PLL, shared by both SIE's.
S
OFTWARE
S
UPPORT
Software is provided in two different configurations: Ethernet drivers or Ethernet plus bridging
software.
The Ethernet drivers run on Windows 95/98/2000 and are miniport device driver software which
emulates a network interface connector. It manages the USB protocol and the PC-to-PC data
flow. The EZ-Link Ethernet device driver is written to the NDIS (Network Driver Interface
Specification) standard and provides a standard Windows interface to the resources of the
hardware. To the end user, EZ-Link appears and behaves like an Ethernet card even though no
physical network interface card is present. Thus, users can use standard Windows interface such
as Windows Explorer, Network Neighborhood and standard file sharing security features. With
this driver, users can use multiple EZ-Links to generate their own private mobile network, with
access to other peripheral devices such as printers appearing as network peripherals.
The Ethernet plus bridging drivers run on Windows 95/98/2000. In addition to the Ethernet
connection capability between multiple EZ-Links, users can connect to corporate LANs using
the PC that has both EZ-Link and a corporate Ethernet connection as a bridge device. With this
capability, users have complete access to corporate LAN resources.
AN2720 Data Sheet Version 1.0
06/07/00
Page 4
EZ-Link (AN2720SC)
A
DDITIONAL
S
OFTWARE
U
TILITIES
Unlike other Host-to-Host devices in the market, Cypress provides an entire suite of software
utilities which enhance the end user experiences. Such utilities include:
Specialized Install procedure. The custom install procedure pioneered by Cypress allows
immediate network operation without the need for the end user to access the Network Icon in
the Control Panel. This makes it easy for "Instant Operation" without the need for the user to
understand any networking jargon. Numerous article reviews rave over this feature.
Make Disk Utility. In case an end user does not have the install CD-ROM in possession, the
end user can still install the necessary drivers to a floppy disk using this Make Disk Utility.
This allows the end user to continue to network to other computers without the need of the
install CD-ROM.
Electronic On-line Users Manual. This slick HTML electronic manual includes everything
with regards to Networking operation in an easy-to-read format. Such Information includes
Getting Started information, installation, various configurations, advanced operations and a
background in Networking.
EZ-Link Network Manager. While the user can use Windows Explorer and Network
Neighborhood to navigate for data transfer and accessing other computers, it may take up to
5 minutes for the system to recognize all computers connected to EZ-Link. With the EZ-
Link Network Manager, the user can access all computers connected to the EZ-Link private
LAN immediately. The interface is intuitive and requires no manual for operation.
AN2720 Data Sheet Version 1.0
06/07/00
Page 5
EZ-Link (AN2720SC)
AN2720
E
NDPOINTS
Figure below illustrates the AN2720 endpoints and how they are connected between two
computers A and B.
15 packet buffer
(15 X 64 bytes)
(A)
EP2
OUT
(B)
EP2
IN
15 packet buffer
(15 X 64 bytes)
(A)
EP2
IN
(B)
EP2
OUT
1 packet buffer
(64 bytes)
(A)
EP3
OUT
(B)
EP3
IN
1 packet buffer
(64 bytes)
(A)
EP3
IN
(B)
EP3
OUT
(A)
EP0
(B)
EP0
(A)
EP1
(B)
EP1
Compu
t
er (A
)
Compu
t
er (B
)
Control
endpoints
Status
Interrupt
AN2720 endpoints and FIFOS
Endpoint zero is the default CONTROL endpoints required by every USB device.
Endpoint 1 is an INTERRUPT endpoint, useful for communicating with the PC driver.
Endpoints 2 and 3 are used to transfer USB BULK data. Endpoint 2 has extensive buffering (15
packets of 64 bytes each) and is designed to transfer high-bandwidth data. Endpoint 3, with a
single packet of buffering, can be used as a higher priority channel for driver communication.
Endpoints 2 and 3 operate similarly to each other, differing only by the amount of buffering
between the computers. Considering endpoint 2, when Computer (A) sends a packet over its
endpoint 2 OUT, the packet is stored in the 15-packet FIFO. If Computer (B) does not send any
IN tokens to its endpoint 2 (to retrieve a packet) by the time fifteen packets have been stored, the
AN2720 NAKS the next OUT packet from Computer (A). This handshake is maintained by both
endpoints 2 and 3, in both directions. When one side is unplugged, all packets are flushed from
the FIFOS, and the AN2720 NAKS all IN and OUT tokens from the attached side.
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