UPD78F9234MC-5A4-A Datasheet, PDF (236/419 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

CHAPTER 13 INTERRUPT FUNCTIONS
Figure 13-7. Interrupt Request Acknowledgment Processing Algorithm
Start
No
××IF = 1?
Yes (Interrupt request generated)
No
××MK = 0?
Yes
IE = 1?
Interrupt request pending
No
Yes
Vectored interrupt
servicing
Interrupt request pending
××IF:
××MK:
IE:
Interrupt request flag
Interrupt mask flag
Flag to control maskable interrupt request acknowledgment (1 = enable, 0 = disable)
Figure 13-8. Interrupt Request Acknowledgment Timing (Example of MOV A, r)
Clock
8 clocks
CPU
MOV A, r
Saving PSW and PC, jump
to interrupt servicing
Interrupt servicing program
Interrupt
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.
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User’s Manual U17446EJ5V0UD