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CHAPTER 16 INTERRUPT AND TEST FUNCTIONS
User’s Manual U11302EJ4V0UM
Figure 16-13. Interrupt Request Acknowledgment Timing (Minimum Time)
Remark
1 clock cycle = 1/f
CPU
(f
CPU
: CPU clock)
Figure 16-14. Interrupt Request Acknowledgment Timing (Maximum Time)
Remark
1 clock cycle = 1/f
CPU
(f
CPU
: CPU clock)
16.4.3 Software interrupt request acknowledgment 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 of the program status word (PSW) and program
counter (PC) are saved in the stacks in that order, the IE flag is reset to 0 and the contents of the vector tables (003EH
and 003FH) are loaded into the PC and branched.
Return from the software interrupt is possible with the RETB instruction.
Caution
Do not use the RETI instruction for returning from the software interrupt.
Instruction
Instruction
PSW and PC save,
jump to interrupt
servicing
6 clocks
Interrupt
servicing
program
8 clocks
7 clocks
CPU processing
××
IF
(××
PR = 1)
××
IF
(××
PR = 0)
Instruction
Divide instruction
PSW and PC save,
jump to interrupt
servicing
6 clocks
Interrupt
servicing
program
33 clocks
32 clocks
CPU processing
××
IF
(××
PR = 1)
××
IF
(××
PR = 0)
25 clocks
Содержание mPD780208 Subseries
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