Datasheet

CHAPTER 17 INTERRUPT FUNCTIONS
User’s Manual U18698EJ1V0UD
449
Figure 17-8. Interrupt Request Acknowledgment Timing (Minimum Time)
8 clocks
7 clocks
Instruction Instruction
PSW and PC saved,
jump to interrupt
servicing
Interrupt servicing
program
CPU processing
××IF
(××PR = 1)
××IF
(××PR = 0)
6 clocks
Remark 1 clock: 1/fCPU (fCPU: CPU clock)
Figure 17-9. Interrupt Request Acknowledgment Timing (Maximum Time)
33 clocks
32 clocks
Instruction Divide instruction
PSW and PC saved,
jump to interrupt
servicing
Interrupt servicing
program
CPU processing
××IF
(××PR = 1)
××IF
(××PR = 0)
6 clocks25 clocks
Remark 1 clock: 1/fCPU (fCPU: CPU clock)
17.4.2 Software interrupt request acknowledgment
A software interrupt acknowledge is acknowledged by BRK instruction execution. Software interrupts cannot be
disabled.
If a software interrupt request is acknowledged, the contents are saved into the stacks in the order of the program
status word (PSW), then program counter (PC), the IE flag is reset (0), and the contents of the vector table (003EH,
003FH) are loaded into the PC and branched.
Restoring from a software interrupt is possible by using the RETB instruction.
Caution Do not use the RETI instruction for restoring from the software interrupt.