DS_FT2232D Datasheet, PDF (50/61 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
Incoming Fast Serial Data
The external device is allowed to send data into the chip if FSCTS is high. On receipt of a Zero start bit on
FSDI, the chip will drop FSCTS on the next positive clock edge. The data from bits 0 to 7 is then clocked
in (LSB first). The next bit determines where the data will be written to. It can go to either channel A or
to channel B. A „0‟ will send it to channel A, providing channel A is enabled for fast serial mode, otherwise
it will go to channel B. A „1‟ will send it to channel B, providing channel B is enabled for fast serial mode,
otherwise it will go to channel A. (Either channel A, or channel B, or both must be enabled as fast serial
mode or the circuit is disabled).
Figure 8.16 Fast Opto-Isolated Serial Data Format - Data input to the FT2232D
Notes:-
(i) Start Bit is always 0.
(ii) Data is sent LSB first.
(iii) The destination bit (DEST) indicates which channel the data should go to. A „0‟ means that it
should go to channel A, a „1‟ means that it should go to channel B.
(iv) The target device should check CTS is high before it sends data. CTS goes low after data bit
0 (D0) and stays low until the chip can accept more data.
Contention
There is a possibility that contention may occur, where the interface goes from being completely idle to
both sending and receiving at the same clock instance. In this case the chip backs off, and allows the
data from the external device to be received.
Data Format
The data format for either direction is:-
1) Zero Start Bit
2) Data bit 0
3) Data bit 1
4) Data bit 2
5) Data bit 3
6) Data bit 4
7) Data bit 5
8) Data bit 6
9) Data bit 7
10) Source/Destination („0‟ indicates channel A; „1‟ indicates channel B)
Reset / Enable
Fast serial mode is enabled by setting the appropriate bits in the external EEPROM. The fast serial mode
can be held in reset by setting a bit value of 10 using the Set Bit Bang Mode command. While this bit is
set the device is held reset - data can be sent to the device, but it will not be sent out by the device until
the device is enabled again. This is done by sending a bit value of 0 using the set bit mode command.
See application note AN2232L-02, “Bit Mode Functions for the FT2232D” for more details and
examples.
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