Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 79)

Publication AG-UM008C-EN-P - February 2005
Configuring MicroLogix 1100/1200/1500 Controllers 3-11
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 let you 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. 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.
For modems that do not supply a CTS signal but still require RTS to be
raised prior to transmission, jumper RTS to CTS and use the shortest
delay possible without losing reliable operation.
Certain modems will drop their carrier link when RTS is set inactive
even though the transmission has not quite been finished. The RTS
Off Delay parameter specifies in 20 millisecond increments the delay
between when the last serial character is sent to the modem and when
RTS is deactivated. This gives the modem extra time to transmit the
last character of a packet.
IMPORTANT
If an RTS Send Delay of 0 is selected, then
transmission starts as soon as CTS is activated. If CTS
does not go active within one second after RTS is
raised, RTS is set inactive and the transmission is
aborted.
ATTENTION
For almost all modem applications, the RTS Off
Delay should be left at 0. Never select an RTS Off
Delay that is greater than the RTS Send Delay in
the other devices on the network, or you may
incur two devices trying to transmit
simultaneously.