DS_FT2232D Datasheet, PDF (48/61 Pages) List of Unclassifed Manufacturers – Future Technology Devices International Ltd

Document No.: FT_000173
FT2232D DUAL USB TO SERIAL UART/FIFO IC Datasheet
Version 2.05
Clearance No.: FTDI# 127
8.7 Fast Opto-Isolated Serial Interface Mode Signal Descriptions and
Interface Configuration
Fast Opto-Isolated Serial Interface Mode provides a method of communicating with an external device
over USB using 4 wires that can have opto-isolators in their path, thus providing galvanic isolation
between systems. If either channel A or channel B are enabled in fast opto-isolated serial mode then the
pins on channel B are switched to the fast serial interface configuration. The I/O interface for fast serial
mode is always on channel B, even if both channels are being used in this mode. An address bit is used
to determine the source or destination channel of the data. It therefore makes sense to always use at
least channel B or both for fast serial mode, but not A own its own.
When either Channel B or Both Channel A and B are configured in Fast Opto-Isolated Serial Interface
mode following IO signal lines are configured as follows :-
Pin#
Signal
Type
Description
40
FSDI
INPUT
Fast serial data input **Note 30
39
FSCLK
INPUT
Clock input to FT2232D chip to clock data in or out.
The external device has to provide a clock signal or
nothing will change on the interface pins. This gives
the external device full control over the interface. It
is designed to be half duplex so that data is only
transferred in one direction at a time. **Note 30
38
FSDO
OUTPUT
Fast serial data output. Driven low to indicate that
the chip is ready to send data.
37
FSCTS
OUTPUT
Clear To Send control signal output
26
SI/WU
INPUT
The Send Immediate / WakeUp signal combines
two functions on a single pin. If USB is in suspend
mode (PWREN# = 1) and remote wakeup is
enabled in the EEPROM , strobing this pin low will
cause the device to request a resume on the USB
Bus. Normally, this can be used to wake up the
Host PC.
During normal operation (PWREN# = 0), if this pin
is strobed low any data in the device TX buffer will
be sent out over USB on the next Bulk-IN request
from the drivers regardless of the pending packet
size. This can be used to optimise USB transfer
speed for some applications. Tie this pin to VCCIO if
not used.
Table 8.14 Fast Opto-Isolated Serial Interface Mode IO Signal Lines Configuration
**Note 30: Pulled up to VCCIO via internal 200K resistors. These pins can be programmed to gently pull
low during USB suspend ( PWREN# = “1” ) by setting this option in the EEPROM.
Fast Opto-Isolated serial interface mode is enabled in the external EEPROM.
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