Watchdog (Bus Monitoring, Plc/Pcs Monitoring) - Siemens SIMOCODE pro System Manual

Standard functions
10.9

Watchdog (Bus monitoring, PLC/PCS monitoring)

Description
The "Watchdog" function block monitors communication with the PLC via
PROFIBUS DP , as well as the operating state of the PLC in the "Remote"
operating mode.
Schematic
Bus monitoring:
With this type of monitoring, the "Trip - Bus" fault is generated if
• "Bus monitoring" is active
• When, in the "Remote" operating mode (mode selector S1=1 and S2=1), the
Cyclic Data transfer between the PLC and SIMOCODE pro is interrupted, e.g.
by the PROFIBUS DP connection being interrupted.
• "Status - Bus o.k." can always be evaluated. If SIMOCODE pro is cyclically
exchanging data with the PLC,
"Status - Bus o.k." is set to "1".
PLC/PCS monitoring:
With this type of monitoring, "Trip - PLC/PCS" is generated if
• "PLC/PCS monitoring" is activated.
• The PROFIBUS DP switches to the "CLEAR" status when in the "Remote"
operating mode (mode selector S1=1 and S2=1).
• The "Status - PLC/PCS in Run" can always be evaluated. If the PROFIBUS DP
is in the "CLEAR" status, the "Status - PLC/PCS in Run" is set to "0".
If the "PLC/PCS monitoring - Input" is connected primarily to the "Cyclic
Receive - Bit 0.7" bit, the status of the PLC is deduced from this bit only.
Cyclic communication
PLC/PCS monitoring - Input
(level sensitive)
Fig. 10-13: "Watchdog (PLC/PCS Monitoring)" function block
Notice
"Bus monitoring" and "PLC/PCS monitoring" can only be effective if the DP
slave address monitoring is activated in the DP master system.
10-24
Watchdog (PLC/PCS monitoring)
Bus/PLC fault - Reset
Bus monitoring
PLC/PCS monitoring
Bus response
Status - PLC/PCS in Run
Status - Bus o.k. (Bus is active)
Trip - Bus
Trip - PLC/PCS
SIMOCODE pro
GWA 4NEB 631 6050-22 DS 03