1. In case material is under the sensor after an e-stop it is assumed that a centering
cycle is busy.
This cycle can be in any of the stages, Leading edge centering, Body centering and
Trailing edge centering.
In case the PLC initiates the switch over between those stages, do not change
the command bits during an Emergency stop, but just raise the hold.
6.8.6 HEARTBEAT sequence
For every conveyor a heartbeat is implemented. The heartbeat is a bit that changes status
every second.
PLC command VVS status
Send (Heartbeat) every second flip value of
bit.
First thing the PLC does after it sees the heartbeat of VVS after a timeout of the Heartbeat
timer, it sends the material parameters. Initially, the status of the Heartbeat timer is
Time‑out (Heartbeat Timer) = true. So every time VVS powers up, the parameters are send
from the PLC to VVS.
IF Time-out(HeartbeatTimer) THEN
HMI should display error message "VVS system down"
VVSDown = true
END IF
IF Not Time-out(HeartbeatTimer) AND VVSDown THEN
VVSDown = false
PLC send parameters
END IF
PARAMETERS
Communication scenarios
6
THINKING FORWARD
VMI Vision System VVS (OL82) VVSX 13.0.12.0, VVSU 3.0.6 / 4 / 2016-07-11 / pd#175592
6-33
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