M16C26 Datasheet, PDF (51/239 Pages) Renesas Technology Corp – 16-BIT CMOS SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/20 SERIES

Udenvdeelropment
Preliminary Specifications Rev. 0.9
Specifications in this manual are tentative and subject to change.
Interrupts
M16C/26 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
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 arithmetic instructions changes O flag:
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 specifying one of software interrupt numbers 0 through 63 and execut-
ing the INT instruction. Software interrupt numbers 0 through 31 are assigned to peripheral I/O inter-
rupts, 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 the software interrupt number
involved.
For software interrupt numbers 0 through 31, the microcomputer saves the stack pointer assignment
flag (U flag) when it accepts an interrupt request. The U flag is changed to “0” and the interrupt stack
pointer (ISP) is selected, and then, the interrupt sequence is executed. When returning from the
interrupt routine, the U flag is returned to the state it was before the interrupt request was accepted.
For software numbers 32 through 63, the U flag is not changed, and so the stack pointer is not
affected.
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Renesas Technology Corp.