M16CSLASH1N datasheet(57/238 Pages) RENESAS

57 / 238 page

Rev.1.00

Oct 20, 2004

page 45 of 222

M16C/1N Group

10. Interrupt

REJ09B0007-0100Z

10.1.2 Software Interrupts

A software interrupt is generated when an instruction is executed. The software interrupts are non-

maskable interrupts.

10.1.2.1 Undefined Instruction Interrupt

The undefined instruction interrupt is generated when the UND instruction is executed.

10.1.2.2 Overflow Interrupt

The overflow interrupt is generated when the INTO instruction is executed 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

10.1.2.3 BRK Interrupt

A BRK interrupt is generated when the BRK instruction is executed.

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10.1.2.4 INT instruction Interrupt

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An INT instruction interrupt is generated when the INT instruction is executed. The INT instruction

can select the software interrupt numbers 0 to 63. The software interrupt numbers 0 to 31 are

assigned to the peripheral function interrupt. Therefore, the microcomputer executes the same

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interrupt routine when the INT instruction interrupt is executed as when a peripheral function inter-

rupt is generated.

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The stack pointer (SP) used for the INT instruction interrupt is dependent on which software inter-

rupt number is involved.

So far as software interrupt numbers 0 to 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 inter-

rupt request. So far as software numbers 32 to 63 are concerned, the stack pointer does not make

a shift.

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