Page top

page-top

Lead Contents

Programmable Relay: Difference between ZEN and PLC Ladder Program Operation

FAQ No. FAQ04322

Primary Contents

Question

ZEN Programmable Relays: Is the operation of the ZEN and Programmable Controller ladder programs different?

Answer

ZEN

ZEN executes the entire ladder program (up to 96 lines) from the first to last line at one time. Each row is executed in order from left to right starting from the left bus bar.

FAQ04322_Fig1

Reference

The time from when processing starts at the bus bar until it returns to the bus bar again (to execute the entire ladder program) is called cycle time.

The ON/OFF status produced by an output contact cannot be used as the input contact status in the same cycle, but it can be used in the next cycle.

The Q0 ON/OFF result is reflected one cycle after MO turns ON or OFF.

FAQ04322_Fig2
FAQ04322_Fig3

OMRON Programmable Controllers

Programmable Controllers execute ladder programs one rung (circuit) at a time, starting with the top rung and executing it in order from the left. When the END instruction is reached, the program is executed again from the first rung.

FAQ04322_Fig4

When the following instructions are executed, Q0 turns ON/OFF at the same time as the other bits.

FAQ04322_Fig5
FAQ04322_Fig6