APPENDIX
Appendix 8. 7906 Group Q & A
Interrupts
Q
After execution of the SEI instruction, a branch is made in an interrupt routin.
Why did this occur?
•
•
Interrupt routine
•
•
•
•
•
•
SEI
LDAB A, #00H
RTI
•
•
•
•
CLI
A
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.
•
•
•
•
← Interrupt request
generated
Interrupt routine
•
•
•
•
SEI
LDAB A, #00H
RTI
•
•
•
•
a
CLI
Note: “Interrupt” described here means “maskable interrupt” which can be disabled by the SEI instruction.
(Refer to section “6.2 Interruput source.”)
7906 Group User’s Manual Rev.2.0
20-106
RENESAS [ RENESAS TECHNOLOGY CORP ]
