M16C6K9 Datasheet, PDF (41/292 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6K9 Group
Interrupt
Software Interrupts
A software interrupt occurs when executing certain instructions. Software interrupts are non-maskable inter-
rupts.
• Undefined instruction interrupt
An undefined instruction interrupt occurs when executing the UND instruction.
• Overflow interrupt
An overflow interrupt occurs when executing the INTO instruction with the overflow flag (O flag) set to “1”.
The following are instructions whose O flag changes by arithmetic:
ABS, ADC, ADCF, ADD, CMP, DIV, DIVU, DIVX, NEG, RMPA, SBB, SHA, SUB
• BRK interrupt
A BRK interrupt occurs when executing the BRK instruction.
• INT interrupt
An INT interrupt occurs when assigning one of software interrupt numbers 0 through 63 and executing the
INT instruction. Software interrupt numbers 0 through 31 are assigned to peripheral I/O interrupts, so ex-
ecuting the INT instruction allows executing the same interrupt routine that a peripheral I/O interrupt does.
The stack pointer (SP) used for the INT interrupt is dependent on which software interrupt number is in-
volved.
So far as software interrupt numbers 0 through 31 are concerned, the microcomputer saves the stack pointer
assignment flag (U flag) when it accepts an interrupt request. If change the U flag to “0” and select the
interrupt stack pointer (ISP), and then execute an interrupt sequence. When returning from the interrupt
routine, the U flag is returned to the state it was before the acceptance of interrupt request. So far as
software numbers 32 through 63 are concerned, the stack pointer does not make a shift.
Rev.1.00 Jun 06, 2003 page 41 of 290