Fail-Safe Blocks
Fail-Safe Systems
A5E00085588-03
8-103
Error Information in Diagnostic Buffer
Error Code (W#16#...) Description
75DAH
Error in the safety data format of inputs S and R (error due to
online modification of the Safety Program or internal CPU
fault)
8.10 IEC Pulse and Counter Blocks
Block Description
F_CTUD Up and down counter
F_TP Timer pulse
F_TON Timer on-delay
F_TOF Timer off-delay
8.10.1 F_CTUD
Function
This block is an edge-controlled up/down counter.
The CV count value responds to rising edges of the inputs CU and CD as well as
to the level of the inputs LOAD and R:
• CU↑: CV is increased by 1.
If the count value reaches the upper limit (32,767), it is not increased any
further.
• CD↑: CV is decreased by 1.
If the count value reaches the lower limit (–32,768), it is not decreased any
further.
• LOAD = 1: CV is preset with the value of the input PV.
The values at the inputs CU and CD are ignored.
• R = 1: CV is reset to 0.
The values at the inputs CU, CD and LOAD are ignored.
If in a cycle there is a rising edge at the input CU and the input CD, the counter
keeps its current value.
The QU output is set if the count value is greater than or equal to the preset value
PV. The output QD is set if the count value is less than or equal to zero.
Startup Characteristics
In the first cycle after a cold or warm restart or in the case of a first call, the counter
is reset.
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