Digi NS7520B-1-C36 Hardware Reference Manual page 237

Bits Access Mnemonic
D22 R/W RTSRX
D21 R/W RL
D20 R/W LL
D19:18 R/W OUT1/OUT2
D17 R/W DTR
Table 85: Serial Channel Control Register A
Reset Description
0 Enable active RTS (only when RX FIFO has space)
Supports hardware handshaking. When RTSRX is set,
the RTS output provides the receiver FIFO almost-full
condition. When the receiver FIFO backs up, the RTS
signal is dropped. The RTS output stalls an external
transmitter from delivering data.
0 Remote loopback
Provides a remote loopback feature. When set to 1, the
TXD transmit output is connected to the RXD receive
input. The RL field immediately echoes receive data
back as transmit data.
Primarily used as test vehicle for external data
equipment.
0 Local loopback
Provides an internal local loopback feature. When set
to 1, the internal receive data stream is connected to
the TXD output signal. This field connects the serial
channel receiver directly to the serial channel
transmitter.
Primarily used as a test vehicle for the serial channel
driver firmware.
0 General-purpose output 1/General-purpose
output 2
The OUT1 and OUT2 fields provide extra,
miscellaneous serial channel control signal outputs.
The OUT1 and OUT2 signals can be routed through
PORTA and PORTC pins using PORTA and PORTC
special function modes.
0 Data terminal ready active
Controls the state of the external data terminal ready
signal.
Setting DTR to 1 causes the DTR output to go
active.
Setting DTR to 0 causes the DTR output to go
inactive.
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