GE 90-30/20/Micro manual Int

4

Example:

In the following example, the PLC is used to keep track of the number of parts contained in a temporary storage area. There are two ways of accomplishing this function using the Series 90- 30/20/Micro instruction set.

The first method is to use an up/down counter pair with a shared register for the accumulated or current value. When the parts enter the storage area, the up counter increments by 1, increasing the current value of the parts in storage by a value of 1. When a part leaves the storage area, the down counter decrements by 1, decreasing the inventory storage value by 1. To avoid conflict with the shared register, both counters use different register addresses. When a register counts, its current value must be moved to the current value register of the other counter.

	_____
%I0003

—— ——+————————————————>UPCTR

%I0001
+—— ——+	+————————+R
%I0009
+—— ——————————+ CONST -+PV
	+00005
		+_____+
		%R0100
	_____
%I0003
—— ——+—————————+MOVE_+
	INT
%I0001
+—— ——+ %R0100 -+IN		Q–%R0104
	LEN
	00001
	_____
		_____
%I0003

—— ——+————————————————>DNCTR

%I0002
+—— ——+	+————————+R
%I0009
+—— ——————————+ CONST -+PV
	+00005
		+_____+
		%R0104
	_____
%I0002
—— ——+—————————+MOVE_+
	INT
%I0003
+—— ——+ %R0104 -+IN		Q-%R0100
	LEN
	00001
	_____

4-24 Series 90-30/20/Micro Programmable Controllers Reference Manual–September 1998 GFK-0467K