Execution Timing; Multiple Interrupt; Precautions - Mitsubishi Electric MELSEC iQ-R Series User Manual

Execution timing

The multiple CPU synchronous interrupt program (I45) is executed at the timing for the fixed scan communication cycle. The
fixed scan communication cycle can be changed through the fixed scan communication setting. ( Page 349 Fixed scan
communication setting)
It is also possible to perform refresh during the multiple CPU synchronous interrupt program (I45) in
execution. ( Page 352 Communication through refresh)

Multiple interrupt

For the multiple interrupt of the multiple CPU synchronous interrupt program, refer to the multiple interrupt function. (
Page 129 Multiple interrupt function)

Precautions

The precautions for the multiple CPU synchronous interrupt program are mentioned below.
• Create a multiple CPU synchronous interrupt program so that it has the execution processing time shorter than the fixed
scan communication cycle. If the interrupt program has the execution processing time equal to or longer than the cycle, the
multiple CPU synchronous interrupt interval cannot be guaranteed. ( Page 116 Operation upon occurrence of an
interrupt factor) The execution time of the multiple CPU synchronous interrupt program (I45) can be monitored using the
RAS setting of the CPU parameter. ( Page 203 Error detection setting)
• To send data successfully in the next fixed scan communication cycle, select "Detect" for "Program Execution Section
Exceed (I45)" in "RAS Setting" of [CPU Parameter]. ( Page 203 Error detection setting) With this setting, when data is
written with the multiple CPU synchronous interrupt program after the host CPU module starts data transfer, SM484
(Execution section excess error flag for multiple CPU synchronization interrupt program) is turned on and the number of
data sending errors in the next cycle is stored in SD484 (Number of execution section excess errors for multiple CPU
synchronization interrupt program). In addition, when the data is written while the data cannot be sent in the fixed scan
communication cycle set in a parameter, an error can be detected. (The CPU module continues its operation.)
Multiple CPU synchronous
interrupt program of the
CPU No.1
Multiple CPU synchronous
interrupt program of the
CPU No.2
(4)
Data communication
section by system
Send data of CPU No.2
(6)
(1) CPU No.1 receives send data (A) of CPU No.2 in the next scan.
(2) CPU No.1 receives send data (B) of CPU No.2 after two scans.
(3) SM484 turns on and SD484 counts up because CPU No.2 continuously executes its program even after the start of data communication.
(4) Send data (A) of CPU No.2 is written.
(5) Send data (B) of CPU No.2 is written.
(6) This data is sent in the next scan because it has been written before data update.
(7) This data is sent after two scans because it has been written after data update.
23 MULTIPLE CPU SYSTEM FUNCTION
364
23.5 Multiple CPU Synchronous Interrupt
Fixed scan communication cycle
(3)
(5)
(7)
Fixed scan communication cycle
(1)
(2)