CHAPTER 16 INTERRUPT FUNCTIONS
Preliminary User’s Manual U16315EJ1V0UD
336
Figure 16-8. Interrupt Request Acknowledgement 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/f
CPU
(f
CPU
: CPU clock)
Figure 16-9. Interrupt Request Acknowledgement 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 clocks
25 clocks
Remark
1 clock: 1/f
CPU
(f
CPU
: CPU clock)
16.4.2 Software interrupt request acknowledgement
A software interrupt request 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.