M16C Datasheet, PDF (53/262 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Preliminary Specifications REV.B
Mitsubishi microcomputers
Specifications in this manual are tentative and subject to change.
M16C / 6N Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Interrupts
Software Interrupts
A software interrupt occurs when executing certain instructions. Software interrupts are non-maskable
interrupts.
• 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
interrupt I/O interrupts, so executing 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
involved.
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.
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