7.5 Half Duplex/Full Duplex selection
Using jumper packs J6 and J8, the channels can be configured to operate
in half duplex mode. This causes the transmitters to be controlled by
either the Data Terminal Ready (DTR) or the Request to Send (RTS)
output from the UART. In half duplex mode, if the UART signal (DTR or
RTS) is asserted (logic 1), the transmitters are enabled for both TxD and
AUXOUT. At the same time, since the inverse of the transmitter enable is
connected to the receiver enable, the receivers are disabled and the signal
lines RXD and AUXIN enter a high-impedence state. If the signal from
the UART is not asserted (logic 0), the transmitter lines enter a
high-impedance state and the receivers are enabled. To operate in
half-duplex DTR mode, configure J6/J8 so that pin 1 is connected to pin 4
and pin 3 is connected to pin 6. To operate in half-duplex RTS mode,
configure J6/J8 so that pins 2 and 5 are connected and pins 3 and 6 are
connected. The transmitters and receivers are always enabled in full
duplex mode. Figure 21 shows how to select half or full duplex
operation.
Half-Duplex(DTR) Operation
Full-Duplex Operation
Half-Duplex(RTS) Operation
TXEN
TXEN
DTR
RTS
2
RXEN
/TXEN
5
TXEN
TXEN
DTR
RTS
RXEN
/TXEN
1
4
1
3
2
TXEN
/TXEN
RXEN
4
5
6
TXEN
DTR
RTS
J6/J8 J6 = Serial0 J8 = Serial1
Figure 21 --- Half or Full Duplex selection on J6, J8
WARNING:
When operating in half duplex mode, the transmitters
must be disabled before receiving any data. Failure to do so may
result in multiple active output drivers being connected together,
which may cause damage to the board, the computer, and the
external device.
7-4
Quatech Inc.
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