Rockwell Automation Publication 2080-UM002N-EN-E - November 2022
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Appendix G Connect to Networks using DF1
DF1 Radio Modem
When you configure the Micro800 controllers for DF1 Radio Modem, the following control line
operation takes effect:
No Handshake Selected
RTS is always inactive. Receptions and transmissions take place regardless of the state of CTS
input. This selection should only be made when the controller is directly connected to another
device that does not require handshaking signals.
Half-Duplex without Continuous Carrier (RTS/CTS) Selected
RTS is activated during transmission and during any programmed delays before or after
transmissions. Programmed delays include RTS Send Delay and RTS Off Delay.
Transmissions require CTS 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 with DCD Handshake Selected
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 DCD input
signal is monitored to determine if transmissions are acceptable. If DCD is active, receptions
are possible.
Transmissions require CTS to be active and DCD to be inactive. If DCD is active at the onset of
transmission, a configured 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.
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.
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.