PLC ladder diagram compilation principle - Database & Sql Blog Articles

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The IL language is very close to assembly language. After encoding, the plc processor can be easily recognized, but the ladder diagram is a graphic element, and the CPU is not easy to recognize, so the ladder diagram is first compiled into the IL language. This article provides a way to recursively compile, and for the sake of imperfections, please forgive me.

In the whole process of ladder diagram compilation, two steps (or functions) are mainly used, one step analyzes the series relationship between blocks, and one step analyzes the parallel relationship between blocks.

Step 0: Initialize the first line of the starting behavior network, starting with the first column and ending with the last column. Then go to step 1.

figure 1

figure 2

(Now in step 2) Then pass a1, a2, a3 to step 1 for serial analysis. According to step 2, after X2 is passed to step 1, the OR command is added, and after X3 is passed to step 1, Add an OR instruction.
A1 enters step 1, and can get a1 only one line, so directly output a1 as
LD X1
A2 is passed to step 1, and you can get
LD X2
OR
A3 can be obtained by passing in step 1.
LD X3
OR
Finally, analyze the instructions, as long as there is
LD Xn
Or
This is combined into OR Xn.
After finishing, get the instruction as:
LD X1
OR X2
OR X3
.
Traverse in turn, and finally get all the instructions as:
LD X1
OR X2
OR X3
LD X4
OR X5
ANB
LD X6
OR X7
ANB
LD X9
OR X10
LD X11
LD X12
ANB
ORB
LD X13
OR X14
LD X15
OR X16
ANB
OR X17
ANB
OUT Y1
In this algorithm, the ladder element is divided into blocks, which is the most critical, so it is necessary to deal with the block of the ladder element. As for how to divide the block, you need to think about it~