Delta DVP-ES2/EX2/SS2/SA2/SX2/SE manual Fuzzy Syntax, Example Better method OK method

DVP-ES2/EX2/SS2/SA2/SX2/SE Operation Manual - Programming

1.7Fuzzy Syntax

Generally, the ladder diagram programming is conducted according to the “up to down and left to right” principle. However, some programming methods not following this principle still perform the same control results. Here are some examples explaining this kind of “fuzzy syntax.”

Example 1:

X0 X2

X1 X3

X4

X5

Better method			OK method
LD	X0	LD		X0
OR	X1	OR		X1
LD	X2	LD		X2
OR	X3	OR		X3
ANB		LD		X4
LD	X4	OR		X5
OR	X5	ANB
ANB		ANB

The two instruction programs can be converted into the same ladder diagram. The difference between Better and OK method is the ANB operation conducted by MPU. ANB instruction cannot be used continuously for more than 8 times. If more than 8 ANB instructions are used continuously, program error will occur. Therefore, apply ANB instruction after a block is made is the better method to prevent the possible errors. In addition, it’s also the more logical and clearer programming method for general users.

Example 2:

X0

X1

X2

X3

	Good method		Bad method
LD	X0	LD	X0
OR	X1	LD	X1
OR	X2	LD	X2
OR	X3	LD	X3

ORB

ORB

ORB

The difference between Good and Bad method is very clear. With longer program code, the required MPU operation memory increases in the Bad method. To sum up, following the general principle and applying good / better method when editing programs prevents possible errors and improves program execution speed as well.

Common Programming Errors

PLC processes the diagram program from up to down and left to right. When editing ladder diagram users should adopt this principle as well otherwise an error would be detected by WPLSoft when compiling user program. Common program errors are listed below:

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