Software Interrupts - Renesas R8C Series User Manual

R8C/1A Group, R8C/1B Group
12.1.2

Software Interrupts

A software interrupt is generated when an instruction is executed. Software interrupts are non-maskable.
12.1.2.1 Undefined Instruction Interrupt
The undefined instruction interrupt is generated when the UND instruction is executed.
12.1.2.2 Overflow Interrupt
The overflow interrupt is generated when the O flag is set to 1 (arithmetic operation overflow) and the INTO
instruction is executed. Instructions that set the O flag are: ABS, ADC, ADCF, ADD, CMP, DIV, DIVU,
DIVX, NEG, RMPA, SBB, SHA, and SUB.
12.1.2.3 BRK Interrupt
A BRK interrupt is generated when the BRK instruction is executed.
12.1.2.4 INT Instruction Interrupt
An INT instruction interrupt is generated when the INT instruction is executed. The INT instruction can select
software interrupt numbers 0 to 63. Software interrupt numbers 4 to 31 are assigned to the peripheral function
interrupt. Therefore, the MCU executes the same interrupt routine when the INT instruction is executed as
when a peripheral function interrupt is generated. For software interrupt numbers 0 to 31, the U flag is saved to
the stack during instruction execution and the U flag is set to 0 (ISP selected) before the interrupt sequence is
executed. The U flag is restored from the stack when returning from the interrupt routine. For software interrupt
numbers 32 to 63, the U flag does not change state during instruction execution, and the selected SP is used.
Rev.1.30 Dec 08, 2006
REJ09B0252-0130
Page 79 of 315
12. Interrupts