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Figure 17-8. Interrupt Request Acknowledgement Timing (Minimum Time)
CPU processing
××IF
(××PR = 1)
××IF
(××PR = 0)
Remark 1 clock: 1/f
CPU
Figure 17-9. Interrupt Request Acknowledgement Timing (Maximum Time)
CPU processing
××IF
(××PR = 1)
××IF
(××PR = 0)
Remark 1 clock: 1/f
CPU
17.4.2 Software interrupt request acknowledgement
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.
CHAPTER 17 INTERRUPT FUNCTIONS
Instruction
(f
: CPU clock)
CPU
Instruction
(f
: CPU clock)
CPU
User's Manual U16899EJ2V0UD
PSW and PC saved,
Instruction
jump to interrupt
servicing
8 clocks
7 clocks
25 clocks
PSW and PC saved,
Divide instruction
jump to interrupt
servicing
33 clocks
32 clocks
6 clocks
Interrupt servicing
program
6 clocks
Interrupt servicing
program
369
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