APPENDIX C DSP FUNCTION

When a MCU which support the DSP function is used, it is necessary to note the treatment of the ACC register (accumulator). Concretely, please note it as follows when you use the following DSP instructions which update ACC register.

- RXv1/RXv2 architecture common instruction
MACHI, MACLO, MULHI, MULLO, RACW, MVTACHI, MVTACLO

- RXv2 architecture instructions
EMACA, EMSBA, EMULA, MACLH, MSBHI, MSBLH, MSBLO, MULLH, MVTACGU, RACL,RDACL, RDACW

In no case does the compiler generate these instructions.

Note also that if the -chkdsp option is specified in the assembler, the DSP function instructions written in a

program are detected as warning.

C.1 When Using DSP Instructions in Tasks and Task Exception Handling Routines

Make settings that include "ACC" for Task context register (context) in System Information (system). As a result, the ACC register is managed independently in each task.

C.2 When Using DSP Instructions in Handlers

If the application contains any tasks or interrupt handlers that use the above-mentioned DSP instructions, it is necessary that all of the interrupt handlers guarantee the ACC register. There are the following two method.

1 ) Use "-save_acc" compiler option

2 ) Specify "ACC" for "pragma_switch" in all interrupt handler definition (Relocatable Vector Information (interrupt_vector[]) and Fixed Vector/Exception Vector Information (interrupt_fvector[])).