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Rev.1.02 Jul 01, 2005 page 57 of 314
REJ09B0126-0102
M16C/6N Group (M16C/6NL, M16C/6NN) 9. Interrupt
Under development
This document is under development and its contents are subject to change.
9.2 Software Interrupts
A software interrupt occurs when executing certain instructions. Software interrupts are non-maskable
interrupts.
9.2.1 Undefined Instruction Interrupt
An undefined instruction interrupt occurs when executing the UND instruction.
9.2.2 Overflow Interrupt
An overflow interrupt occurs when executing the INTO instruction with the O flag set to “1” (the operation
resulted in an overflow). The following are instructions whose O flag changes by arithmetic:
ABS, ADC, ADCF, ADD, CMP, DIV, DIVU, DIVX, NEG, RMPA, SBB, SHA, SUB
9.2.3 BRK Interrupt
A BRK interrupt occurs when executing the BRK instruction.
9.2.4 INT Instruction Interrupt
An INT instruction interrupt occurs when executing the INT instruction. Software interrupt Nos. 0 to 63 can
be specified for the INT instruction. Because software interrupt Nos. 1 to 31 are assigned to peripheral
function interrupts, the same interrupt routine as for peripheral function interrupts can be executed by
executing the INT instruction.
In software interrupt Nos. 0 to 31, the U flag is saved to the stack during instruction execution and is set
to “0” (ISP selected) before executing an interrupt sequence. The U flag is restored from the stack when
returning from the interrupt routine. In software interrupt Nos. 32 to 63, the U flag does not change state
during instruction execution, and the SP then selected is used.