Device Function

A processor can use the status lines TXE# and RXF# in either a polled or interrupt manner.

The TXE# line will go active LOW indicating that there is room available in the 384 bytes transmit

buffer for the processor to place another byte for transmission over the USB bus. The RXF# line

will go active LOW when there is at least one byte available in the 128 byte FIFO for the

processor to read.

To write data into the transmit FIFO, the following procedure should be used: With the WRITE

line LOW, the processor places the data on lines D0-D7. The processor then strobes the WRITE

line by bringing it HIGH for a minimum of 50 ns, and then completes the cycle by bringing the

WRITE line back LOW.

To read data from the receive FIFO, the processor drives the RD# line LOW. After a maximum

time of 30 ns, valid data will be driven on lines D0-D7. The processor reads the data and then

drives the RD# line back inactive HIGH.

For USB powered controls, USB power would be fed into Pin 22. The filtered output provided

at Pin 23 would then be tied to Pin 24 (Vcc). This power (+5volts) can be used to power other

circuits in the design, up to the maximum current draw per USB device. For USB specifications

see: www.usb.org/developers.

For System powered controls, +5 volts can be directly fed into Pin 24. Pins 22-23 are left

unconnected. Alternatively system power can be fed into Pin 22. Pin 23 would then be tied to Pin

24 for extra system power filtering. In this case USB power is never connected to the device.

USB power and alternate System power sources should not be tied together, except for

common grounding (GND).

The USB245 is a ‘slave’ or ‘peripheral’ device to a ‘master’ or ‘host’ USB controller such as a

PC running Windows 98/2000. The host must have appropriate drivers running to access the

USB245. Drivers are available for Windows and Mac Systems.

Addition Information

USB Cable color codes: Red

5 Volts, Black

GND, Green

DP, White

DM

Schematic Usage

See appendix for a simple example using the USB245 with the Ubicom SX-28.

Pin Orientation

Pin 1

Vcc

GND

(version 1.0)

Software Drivers Supplied & Supported by: Future Technology Devices International Ltd. (FTDI).

http://www.ftdichip.com