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CHAPTER3 CPU MODULE OPERATION

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3.2  I/O Refresh (Refresh Processing with Input/Output Modules)

The CPU module performs the following before sequence program operations.

 • On/off data input from the input module or intelligent function module to the CPU module
 • On/off data output from the CPU module to the output module or intelligent function module

When the constant scan time is set, I/O refresh is performed after the constant scan waiting time has 
elapsed.

 

(I/O refresh is performed at each constant scan cycle.)

3.3  Program Operation

The CPU module sequentially executes the program stored in the module from the step 0 to the END or 
FEND instruction.(

 CHAPTER 2)

3.4  END Processing

The CPU module performs refresh processing with network modules and communication with external 
devices.
END processing includes the following.

 • Refresh with network modules (

 CHAPTER 10)

 •

Auto refresh with intelligent function module 

(

 • Intelligent function module dedicated instruction processing (

 • Device data latch processing (

 • Service processing (

 • Watchdog timer reset (

 Section 6.16)

 • Auto refresh between multiple CPU modules (

 QCPU User's Manual (Multiple CPU System))

 • Device data collection using the sampling trace function (only when trace point is set to every scan (after 

END instruction execution)) (

 • Self-diagnostics processing (

 • Special relay/special register value setting (only for those that should be set during END processing)

(

 CHAPTER 12)

When the constant scan function (

 Section 6.2) is used, the results of processing performed in 

END processing are held for the period between after END processing is completed and until the 
next scan starts.