Siemens SIMATIC S7-200 System Manual page 173

Example: Interrupt Instructions
M
A
I
N
I
N
T
0
Example: Timed Interrupt for Reading the Value of an Analog Input
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I
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S
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R
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Network 1 //On the first scan:
//1. Define interrupt routine INT_0 to
// be a falling-edge interrupt for I0.0
//2. Globally enable interrupts.
LD SM0.1
ATCH INT_0, 1
ENI
Network 2 //If an I/O error is detected,
//disable the falling-edge interrupt for I0.0.
//This network is optional.
LD SM5.0
DTCH 1
Network 3 //When M5.0 is on,
//disable all interrupts.
LD M5.0
DISI
Network 1 //I0.0 falling-edge interrupt routine:
//Conditional return based on an I/O error.
LD SM5.0
CRETI
Network 1 //On the first scan, call subroutine 0.
LD SM0.1
CALL SBR_0
Network 1 //1. Set the interval for the timed interrupt 0 to 100 ms.
//2. Attach timed interrupt 0 (Event 10) to INT_0.
//3. Global interrupt enable.
LD SM0.0
MOVB 100, SMB34
ATCH INT_0, 10
ENI
Network 1 //Read the value of AIW4 every 100 ms
LD SM0.0
MOVW AIW4, VW100
S7-200 Instruction Set Chapter 6
159