10.9.5.1 Parameters of the Down Counter Function
Input/ Output
Choices
Description
address R
The function uses three consecutive words
(registers) of %R memory to store the following:
• Current value (CV) = word 1.
• Preset value (PV) = word 2.
• Control word = word 3.
Do not use this address with another down
counter, up counter, or any other instruction or
improper operation will result.
Careful: Overlapping references will result in
erratic counter operation.
enable flow
On a positive transition of enable, the current
value is decremented by one.
R flow
When R receives power flow, it resets the current
value to the preset value.
PV
I, Q, M, T, G, R, AI, AQ,
constant, none
PV is the value to copy into the counter’s preset
value when the counter is enabled or reset.
Q
flow, none
Output Q is energized when the current value is
less than or equal to zero.
10.9.5.2 Example 1:
In the example, the down counter identified as COUNTP counts 500 new parts before
energizing output %Q0005.
10.9.5.3 Example 2: Keeping Track of Parts in a Temporary
Storage Area
The following example shows how the PLC can keep track of the number of parts in a
temporary storage area. It uses an up/down counter pair with a shared register for the
accumulated or current value. When parts enter the storage area, the up counter increases
the current value of the parts in storage by 1. When a part leaves the storage area, the
down counter decrements by 1, decreasing the inventory storage value by 1. The two
counters use different register addresses. When a register counts, its current value must be
moved to the current value register of the other counter.
Instruction Set Reference GFK-1503E User Manual 193
For public disclosure
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