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Rockwell Automation Publication 5069-UM003B-EN-P - January 2020
Chapter 3
Compact 5000 I/O Serial Module Features
DF1 Half Duplex Master
When configuring for DF1 half-duplex master, the following control line
operation takes effect:
• No Handshaking Selected—DTR is always active and RTS is always
inactive. Receptions and transmissions take place regardless of the states
of DSR, CTS, or DCD inputs. Only make this selection when the
processor is directly connected to another device that does not require
handshaking signals.
• Full-Duplex Modem Selected—DTR and RTS are always active except at
the following times:
– If DSR goes inactive, both DTR and RTS are dropped for 1 to 2
seconds then reactivated. While DSR is inactive, the state of DCD
is ignored. Neither receptions or transmissions are performed.
– If DCD goes inactive while DSR is active, then receptions are not
allowed. If DCD remains inactive for 9 to 10 seconds, then DTR
is set inactive. If DSR remains active, then DTR is raised again in
5 to 6 seconds.
Reception requires DSR and DCD to be active. Transmission requires all three
inputs (CTS, DCD, and DSR) to be active.
• Half-Duplex Modem without Continuous Carrier Selected—DTR is
always active and RTS is only active during transmissions (and any
programmed delays before and after transmissions). The serial module
does not monitor DCD.
If DSR goes inactive, RTS is dropped. While DSR is inactive, neither receptions
or transmissions are performed.
Reception requires DSR to be active. Transmission requires two inputs, CTS and
DSR, to be active.
