Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 146)

Publication AG-UM008C-EN-P - February 2005
4-8 Configuring SLC 5/03, 5/04, and 5/05 Processors
Half-Duplex with Continuous Carrier Selected
DTR is always active. RTS is activated during transmission and during
any programmed delays before or after transmissions. Programmed
delays include RTS Send Delay and RTS Off Delay. The DSR input
signal must remain active for transmissions or receptions to occur. The
modem lost bit is set whenever DSR is inactive. The DCD input signal
is ignored.
Transmission requires CTS and DSR to be active. If CTS is inactive at
the onset of transmission, one second will be provided to wait for CTS
to become active before the message packet is discarded.
Half-Duplex without Continuous Carrier Selected
DTR is always active. RTS is activated during transmissions and during
any programmed delays before and after transmissions. Programmed
delays include RTS Send Delay and RTS Off Delay. The DSR input
signal must remain active for transmissions or receptions to occur. The
modem lost bit is set whenever DSR is inactive. The DCD input signal
is monitored to determine if transmissions are acceptable. If DCD is
active, receptions are possible.
Transmission requires CTS and DSR to be active and DCD to be
inactive. IF DCD is active at the onset of transmission, a configurable
delay (DCD Wait Delay) will wait for DCD to become inactive before
discarding the packet. If CTS is inactive at the onset of transmission,
one second will be provided to wait for CTS to become active before
the message packet is discarded.
Configuring DF1
Half-Duplex Channel 0
Parameters RTS Send Delay and RTS Off Delay
Through your programming software, the parameters RTS Send Delay
and RTS Off Delay give you the ability to set how long RTS is on prior
to transmission, as well as how long to keep it on after transmission is
complete. These parameters only apply when you select half-duplex
modem with or without continuous carrier. For maximum
communication throughput, leave these parameters at zero.
For use with half-duplex modems that require extra time to
turnaround or key-up their transmitter even after they have activated
CTS, the RTS Send Delay specifies (in 20 millisecond increments) the
amount of delay time after activating RTS to wait before checking to
see if CTS has been activated by the modem. If CTS is not yet active,
RTS remains active, and as long as CTS is activated within one second,
the transmission occurs. After one second, if CTS is still not activated,
then RTS is set inactive and the transmission is aborted.