UPD78F0838 Renesas Electronics Corporation., UPD78F0838 Datasheet - Page 736

• Manufacturer Part Number: UPD78F0838
• Description: 8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

19.4 Interrupt Servicing Operations
19.4.1 Maskable interrupt acknowledgement
corresponding to that interrupt request is cleared to 0. A vectored interrupt request is acknowledged if interrupts are
in the interrupt enabled state (when the IE flag is set to 1).
acknowledged during servicing of a higher priority interrupt request (when the ISP flag is reset to 0). The times from
generation of a maskable interrupt request until interrupt servicing is performed are listed in Table 19-4 below.
specified in the priority specification flag is acknowledged first. If two or more interrupts requests have the same
priority level, the request with the highest default priority is acknowledged first.
PC, the IE flag is reset (0), and the contents of the priority specification flag corresponding to the acknowledged
interrupt are transferred to the ISP flag. The vector table data determined for each interrupt request is the loaded into
the PC and branched.
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A maskable interrupt becomes acknowledgeable when the interrupt request flag is set to 1 and the mask (MK) flag
For the interrupt request acknowledgement timing, see Figures 19-8 and 19-9.
If two or more maskable interrupt requests are generated simultaneously, the request with a higher priority level
An interrupt request that is held pending is acknowledged when it becomes acknowledgeable.
Figure 19-7 shows the interrupt request acknowledgement algorithm.
If a maskable interrupt request is acknowledged, the contents are saved into the stacks in the order of PSW, then
Restoring from an interrupt is possible by using the RETI instruction.
Note If an interrupt request is generated just before a divide instruction, the wait time becomes longer.
Remark 1 clock: 1/f
Table 19-4. Time from Generation of Maskable Interrupt until Servicing
When
When
CPU
(f
CPU
PR = 0
PR = 1
: CPU clock)
CHAPTER 19 INTERRUPT FUNCTIONS
Preliminary User’s Manual U19748EJ1V0UD
7 clocks
8 clocks
Minimum Time
However, a low-priority interrupt request is not
32 clocks
33 clocks
Maximum Time
Note