Standard Function Blocks

Introduction

The IEC 61131-3 standard defines a number of function blocks, which are supported in Fernhill SCADA:

Function Block Type	Keywords	Explanation
Bistable	SR, RS	Set and reset dominant bistables.
Rising Edge Detector	R_TRIG	Rising edge detector.
Falling Edge Detector	F_TRIG	Falling edge detector.
Up Counter	CTU	Counts up from zero to a preset value.
Down Counter	CTD	Counts down from a preset value to zero.
Pulse Timer	TP	Generate a fixed duration pulse.
On Delay Timer	TON	Turn an output on after a delay.
Off Delay Timer	TOF	Turn an output off after a delay.

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For the meaning of terms used in Fernhill SCADA.