330 Rockwell Automation Publication 2080-UM002M-EN-E - April 2022
Appendix G Connect to Networks using DF1
Configure DF1 Half-Duplex
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.
Configure a Standard-Mode
DF1 Half-Duplex Master
Station
Choose standard mode if you want to query slave stations for information
based upon user-configured polling ranges. This mode is used most often in
general point-to-multipoint configurations.
To configure the controller as a master station using standard-
communication, place the controller into program mode and follow the steps
below using your programming software:
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.
1. To bring up the configuration page, click
Serial Port.
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