Rockwell Automation Publication 5069-UM003B-EN-P - January 2020 43
Compact 5000 I/O Serial Module Features Chapter 3
Modem Control Line Operation
The following explains the operation of the serial module when you configure the
RS-232 channel for the following applications.
DF1 Full-Duplex
When configured for DF1 full-duplex, the following control line operation
takes effect:
• No Handshaking Selected—DTR is always active (high) and RTS is
always inactive (low). Receptions and transmissions take place regardless
of the states of DSR, CTS, or DCD inputs. Only make this selection when
the serial module is directly connected to another device that does not
require handshaking signals.
• Full-Duplex Modem Selected—DTR and RTS are always active except:
– 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, DTR is set
inactive. 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.
DF1 Half-Duplex Slave
When configured for DF1 half-duplex slave, 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.
• Half-Duplex Modem with Continuous Carrier Selected—DTR is always
active and RTS is only activated during transmissions (and any
programmed delays before or after transmissions). The handling of DCD
and DSR are the same as with Full-Duplex Modem. Reception requires
DSR and DCD to be active. Transmissions require CTS, DCD, and DSR
to be active.
• Half-Duplex Modem without Continuous Carrier Selected—This is the
same as Half-Duplex Modem with Continuous Carrier except monitoring
of DCD is not performed. DCD is still required for receptions, but is not
required for transmissions. Transmissions still require CTS and DSR.
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