m37905 Renesas Electronics Corporation., m37905 Datasheet - Page 545

• Manufacturer Part Number: m37905
• Description: Mitsubishi 16-bit Single-chip Microcomputer 7700 Family / 7900 Series
• Manufacturer: Renesas Electronics Corporation.

APPENDIX
Appendix 8. 7905 Group Q & A
20-114
Note: “Interrupt” described here means “maskable interrupt” which can be disabled by the SEI instruction.
After execution of the SEI instruction, a branch is made in an interrupt routin.
Why did this occur?
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.):
A
Q
• No interrupt request is accepted.
• No branch to the interrupt routine is made.
(Refer to section “6.2 Interruput source.”)
SEI
LDAB A, #00H
CLI
SEI
LDAB A, #00H
CLI
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generated
Interrupt request
7905 Group User’s Manual Rev.1.0
a
Interrupt routine
RTI
Interrupt routine
RTI
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Interrupts