7906 datasheet(511/531 Pages) RENESAS

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APPENDIX

Appendix 8. 7906 Group Q & A

7906 Group User’s Manual Rev.2.0

20-106

After execution of the SEI instruction, a branch is made in an interrupt routin.

Why did this occur?

•

SEI

LDAB A, #00H

•

CLI

Interrupt routine

•

RTI

•

SEI

LDAB A, #00H

•

CLI

Interrupt routine

•

RTI

← Interrupt request

generated

When an interrupt request is generated before the SEI instruction is executed, this interrupt request

may be accepted immediately before the execution of the SEI instruction. (This acceptance occurs

depending on the timing when that interrupt request occurs.) In this case, a branch to the interrupt

routine is made immediately after execution of the SEI instruction.

Accordingly, the interrupt routine which is executed immediately after the SEI instruction is due to an

interrupt request generated before execution of the SEI instruction. Note that, in the routine ( a ) which

should not accept the interrupt request, the following occur. (This routine follows the SEI instruction.):

• No interrupt request is accepted.

• No branch to the interrupt routine is made.

Note: “Interrupt” described here means “maskable interrupt” which can be disabled by the SEI instruction.

(Refer to section “6.2 Interruput source.”)

Interrupts

7906 Datasheet(PDF) 511 Page - Renesas Technology Corp