Delta DVP-ES2 - Manual (Page 20)

D V P - E S 2 / E X 2 / S S 2 / S A2 / S X 2 / S E O p e r a t i o n M a n u a l - P r o g r a m m i n g
1-12
1.7 Fuzzy 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:
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
X0 X2 X4
X5 X3 X1
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:
Good method Bad method
LD X0 LD X0
OR X1 LD X1
OR X2 LD X2
OR X3 LD X3
ORB
ORB
X0
X1
X2
X3
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: