261
CHAPTER 15 INTERRUPT FUNCTIONS
Preliminary User’s Manual U16035EJ1V0UM
33 clocks
32 clocks
Instruction
Divide instruction
PSW and PC save,
jump to interrupt
servicing
Interrupt servicing
program
CPU processing
××
IF
(
××
PR = 1)
××
IF
(
××
PR = 0)
6 clocks
25 clocks
8 clocks
7 clocks
Instruction
Instruction
PSW and PC save,
jump to interrupt
servicing
Interrupt servicing
program
CPU processing
××
IF
(
××
PR = 1)
××
IF
(
××
PR = 0)
6 clocks
Figure 15-12. Interrupt Request Acknowledge Timing (Minimum Time)
Remark
1 clock: 1/f
CPU
(f
CPU
: CPU clock)
Figure 15-13. Interrupt Request Acknowledge Timing (Maximum Time)
Remark
1 clock: 1/f
CPU
(f
CPU
: CPU clock)
15.4.3 Software interrupt request acknowledge operation
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 PC and branched.
Return from a software interrupt is possible with the RETB instruction.
Caution
Do not use the RETI instruction for returning from the software interrupt.