Mitsubishi Q2ACPU, User Manual

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App - 129
APPENDICES
Appendix 4.11 Index Register Processing
For QnACPU, the contents of index registers change when program processing transfers
between the main sequence program and interrupt programs.
• Transfer of program processing from main sequence program to interrupt program
The contents of the index registers of the main sequence program are saved, and
then these contents are passed to the interrupt program.
• Transfer of program processing from interrupt program to main sequence program
The index registers in the interrupt program are cleared, and the saved main
sequence program contents are written to them.
For ACPU, processing differs according to the CPU module type.
• The processing for AnACPU and AnUCPU is the same as for QnACPU, and no
program modification is required after conversion.
• In the case of AnCPU, AnNCPU, and A3HCPU, when program processing is
transferred from an interrupt program to the main program, the data updated in the
interrupt program are passed on to the main program.
When passing a value written to the index register in an interrupt program on to the
main sequence program, for example, modify the program so that the value is passed
on via a data register.