S5 AWL Command: ZR (Count Down)

ZR decrements a counter by 1 on each rising edge of the VKE. The counter stops at 0 — it does not go negative. Counter range is 0–999 (BCD).

Syntax#

U   E 0.0          // Count pulse
ZR  Z n            // Decrement counter n

S7 Equivalent#

Code Example — Batch Counter (count down from preset)#

// Set preset
U   E 0.1          // Load condition
L   KZ 100         // Preset = 100 parts
S   Z 2

// Count down
U   E 0.0          // Part sensor
ZR  Z 2

// Check if batch complete (counter = 0)
UN  Z 2            // TRUE when Z2 = 0
=   A 4.0          // Batch complete signal

Combined Up/Down Counter#

A single counter can use both ZV and ZR:

U   E 0.0          // Count up input
ZV  Z 3

U   E 0.1          // Count down input
ZR  Z 3

Related: ZV (Count Up)#

Part of the S5 AWL Command Reference. Maintained by PLCcheck.ai.

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