PLC command list

PLC command list

## 1. Standard contacts LD, A, O, LDN, AN, ON,

LD, fetch instructions. Indicates a normally open contact instruction connected to the input bus, that is, the start of the normally open contact logic operation.

LDN, negate the instruction. Indicates a normally closed contact instruction connected to the input bus, that is, the start of a normally closed contact logic operation.

A, with instructions. For series connection of a single normally open contact.

AN, and non-commands. For series connection of a single normally closed contact.

O, or instructions. For parallel connection of a single normally open contact.

ON, or non-command. For parallel connection of a single normally closed contact.

2. Positive and negative transitions ED, EU

ED, after detecting a positive transition (from OFF to ON), allow the power flow to be turned on one scan cycle.

EU, after detecting a negative transition (from ON to OFF), let the power flow be turned on for one scan cycle.

3. Output =

=, when the output instruction is executed, the specified parameter bit in the image register is turned on.

4. Set and reset instructions S, R

S, when executing the set (set to 1) instruction, it starts from the address parameter specified by bit or OUT N points are all set.

R, when executing the reset (set to 0) instruction, N points starting from the address parameter specified by bit or OUT are reset.

The number of set and reset points can be 1-255. When using the reset instruction, if the bit or OUT specifies T or C, the timer or counter will be reset and the current value will be cleared. zero.

5. No operation instruction NOP

NOP instruction does not affect the execution of the program, and the execution number is N (1-255).

What is PLC?

PLC is the abbreviation of "Programmable Controller". Originally, the programmable controller (Progammadble Controller) was abbreviated as PC, but in order to avoid confusion with the abbreviation PC (Personal Computer), the programmable controller was called PLC (Progammadble Logic Controller). It can be seen that PLC is a member of the computer family and is a microcomputer mainly used in the field of industrial automatic control.

The basic components of PLC mainly include

Central Processing Unit (CPU), Memory (RAM, ROM), Input and Output Unit (I/O), power supply and programmer and other parts.

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