m37905 Renesas Electronics Corporation., m37905 Datasheet - Page 542

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

If an interrupt request (b) occurs while an interrupt routine (a) is executed, is it true that the main
routine is not executed at all after the execution of the interrupt routine (a) is completed until the
execution of the INTACK sequence for the next interrupt (b) starts?
An interrupt request is sampled by a sampling pulse generated synchronously with the CPU’s op-code
fetch cycle.
(1) If the next interrupt request (b) occurs before sampling pulse
Conditions:
(2) If the next interrupt request (b) occurs immediately after sampling pulse
Q
A
Flag I is cleared to “0” by executing the RTI instruction.
The interrupt priority level of interrupt (b) is higher than IPL of the main routine.
The interrupt priority detection time = 2 cycles of f
ated, the microcomputer executes the INTACK sequence for (b) without executing the main routine.
(No instruction of the main routine is executed.) It is because that sampling is completed while
executing the RTI instruction.
microcomputer executes one instruction of the main routine before executing the INTACK
sequence for (b). It is because that the interrupt request is sampled by the next sampling
pulse
Sampling pulse
Sequence of
execution
Sampling pulse
.
Interrupt routine (a)
RTI instruction
Interrupt routine (a)
Interrupt routine (a)
Interrupt request (b)
RTI instruction
7905 Group User’s Manual Rev.1.0
RTI instruction
Main routine
Interrupt request (b)
?
One instruction executed
Main routine
sys
INTACK sequence for interrupt (b)
Appendix 8. 7905 Group Q & A
INTACK sequence
for interrupt (b)
for the RTI instruction is gener-
INTACK sequence
for interrupt (b)
APPENDIX
is generated, the
Interrupts
20-111