Document No.: FT_000288
FT232H SINGLE CHANNEL HI-SPEED USB TO MULTIPURPOSE UART/FIFO IC
Datasheet Version 1.8
Clearance No.: FTDI #199
4.9.1 Outgoing Fast Serial Data
To send fast serial data out of the FT232H, the external device must drive the FSCLK clock. If the FT232H
has data ready to send, it will drive FSDO output low to indicate the start bit. It will not do this if it is
currently receiving data from the external device. This is illustrated in Figure 4.18
FSCLK
0
Start
Bit
D0
D1
D2
D3
D4
D5
D6
D7
SRCE
Source
Bit
FSDO
Data Bits - LSB first
Figure 4.18 Fast Serial Interface Output Data
Notes :-
1. The first bit output (Start bit) is always 0.
2. FSDO is always sent LSB first.
3. The last serial bit output is the source bit (SRCE) is always 0.
4. If the target device is unable to accept the data when it detects the START bit, it should stop the
FSCLK until it can accept the data.
4.9.2 Incoming Fast Serial Data
An external device is allowed to send data into the FT232H if FSCTS is high. On receipt of a zero START
bit on FSDI, the FT232H will drop FSCTS on the next positive clock edge. The data from bits 0 to 7 are
then clocked in (LSB first). The last bit (DEST) determines where the data will be written to. This bit is
always 0 with the FT232H. This is illustrated in Figure 4.19
FSCTS
FSCLK
0
D0
D1
D2
D3
D4
D5
D6
D7
DEST
FSDI
Start
Bit
Destination
Bit
Data Bits - LSB first
Figure 4.19 Fast Serial Interface Input Data
Notes:-
1. The first bit input (Start bit) is always 0.
2. FSDI is always received LSB first.
3. The last received serial bit is the destination bit (DEST) is always 0.
4. The target device should ensure that FSCTS is high before it sends data. FSCTS goes low after
data bit 0 (D0) and stays low until the chip can accept more data.
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