CHAPTER 13 INTERRUPT FUNCTIONS
User’s Manual U17446EJ3V1UD
231
Figure 13-7. Interrupt Request Acknowledgment Processing Algorithm
Start
××
IF = 1?
××
MK = 0?
IE = 1?
Vectored interrupt
servicing
Yes (Interrupt request generated)
Yes
Yes
No
No
No
Interrupt request pending
Interrupt request pending
××
IF:
Interrupt request flag
××
MK: Interrupt mask flag
IE:
Flag to control maskable interrupt request acknowledgment (1 = enable, 0 = disable)
Figure 13-8. Interrupt Request Acknowledgment Timing (Example of MOV A, r)
Clock
CPU
Interrupt
MOV A, r
Saving PSW and PC, jump
to interrupt servicing
8 clocks
Interrupt servicing program
If an interrupt request flag (
××
IF) is set before an instruction clock n (n = 4 to 10) under execution becomes n
−
1,
the interrupt is acknowledged after the instruction under execution is complete. Figure 13-8 shows an example of the
interrupt request acknowledgment timing for an 8-bit data transfer instruction MOV A, r. Since this instruction is
executed for 4 clocks, if an interrupt occurs for 3 clocks after the instruction fetch starts, the interrupt acknowledgment
processing is performed after the MOV A, r instruction is executed.
Содержание 78K0S/KB1+
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