Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 145)

Publication AG-UM008C-EN-P - February 2005
Configuring SLC 5/03, 5/04, and 5/05 Processors 4-7
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. The modem lost bit (S:5/14) is turned
on immediately. While DSR is inactive, the state of DCD is
ignored. Neither receptions nor 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. At this point, the modem lost bit is also set. 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. Whenever DSR and
DCD are both active, the modem lost bit is reset.
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
processor does not monitor DCD.
If DSR goes inactive, RTS is dropped. The modem lost bit (S:5/14) is
turned on immediately. While DSR is inactive, neither receptions nor
transmissions are performed.
Reception requires DSR to be active. Transmission requires two
inputs, CTS and DSR, to be active. Whenever DSR is active, the
modem lost bit is reset.
DF1 Radio Modem
When you configure the SLC 5/03, SLC 5/04, and SLC 5/05 processors
for DF1 Radio Modem, 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. This selection should only be made when the processor is
directly connected to another device that does not require
handshaking signals.