CCJIMUNICATIONS SECTION 6.4
6.4.7.5
6.4.8
6,4.8.1
6.4.8.2
DTR pin 20 (Data Terminal Ready) Ouptut from HUNTER
This signal, selected on the transmit menu, is provided to
enable modems that require DTR to be present before generating
carrier.
If selected (DTR-y), DTR will go to the active (+ve) state if
either transmission or reception is attempted from the HUNTER.
If not selected (DTR-n), DTR will only be active if transmission
from the HUNTER is attempted.
DTR can also be controlled by the communications power supply
port 132 (see section 9.8), INVCON. DTR is active when the
inverter is on.
Timeouts
Automatic communication timeouts are provided to signal to user
programs that the communications lines are quiescent. Separate
timeouts are user-selectable for both transmit and receive
channels, The timeouts are designed for use with the Basic
ONCOMMS statement (see section 5.16,3), but can also be invoked
manually or by machine code programs. The error number is
available in the location COMERR (see section 9,7, page 9-38).
The timeouts have a range of
10 - 60 seconds in 10 second steps
and are controlled by memory locations RXTOAF and TXTOAF ( see
section 9,7, page 9-38), These locations can be read or written
.to by user programs. When set to O (cleared), the timeouts have
no effect. When set, they have the following effect:
RXTOAF
Will cause a 'communications error' if the receive line is
quiescent for more than the selected period. Reception of any
character, or noise, will reset the timeout. The timeout is
initiated by a request for serial input data through a Basic
'LINPUT' or similar statement.
If no attempt is made to read
the input communications buffer, the timeout will not occur.
TXTOAF
Will cause a 'communications error' if the HUNTER is inhibited
by the hardware handshake lines CTS (Clear to send) or DSR (Date
set ready),
If either line inhibits transmission frorr, the
HUNTER, a 'communications error' will occur aft.er the specified
time.
VER. V09F PAGE 6 - 10
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