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Jack H.Integration and automation of manufacturing systems.2001.pdf
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page 203

buffer

ARL(channel, dest, control, length) - will get characters from an ASCII buffer

ASC(string, start, string, result) - this will look for one string inside another AWT(channel, string, control, length) - will write characters to an ASCII out-

put

• An example of this function is given below,

• Try the problem below,

Add the following numbers and store the results in ST10:2

ST10:0 “100”

ST10:1 “10”

ST10:2

7.20 DESIGN TECHNIQUES

7.20.1 State Diagrams

• We can implement state diagrams seen in earlier sections using many of the advanced func-

page 204

tion discussed in this section.

Most PLCs allow multiple programs that may be used as subroutines. We could implement a block logic method using subroutine programs.

Consider the state diagram below and implement it in ladder logic. You should anticipate what will happen if both A and C are pushed at the same time.

STA

STC

B

D

A

C

 

STB

 

first scan

page 205

PROGRAM 2

first scan

L STB

U STA

U STC

STA

JSR program 3

STB

JSR program 4

STC

JSR program 5