Fail-Safe Blocks
Fail-Safe Systems
A5E00085588-03
8-107
8.10.3 F_TON
Function
The block delays a rising edge by the time PT.
A rising edge at the input IN results in a rising edge at the output Q after the time
PT has elapsed. Q remains set until the input IN changes to 0.
If the input IN changes to 0 before PT has elapsed, Q remains at 0.
The output ET indicates the time that has elapsed since the last rising edge at the
input IN, but only up to the value of the input PT. ET is reset if the input IN changes
to 0.
If PT < 0, the outputs Q and ET are reset.
Timing Diagram
scasc
Q
IN
PT
ET
PT PT
Startup Characteristics
In the first cycle after a cold or warm restart or in the case of a first call, the timer is
reset.
I/Os
Name Data Type Explanation Default
Inputs:
IN F_BOOL Start input 0
PT F_TIME Length of the delay T#0 ms
Outputs:
Q F_BOOL Pulse output 0
ET F_TIME Elapsed time T#0 ms
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