Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 147)

Publication AG-UM008C-EN-P - February 2005
Configuring SLC 5/03, 5/04, and 5/05 Processors 4-9
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.
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.
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.
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.