R8C/20 Group, R8C/21 Group 12. Interrupts
Rev.2.00 Aug 27, 2008 Page 111 of 458
REJ09B0250-0200
12.6.4 Changing Interrupt Sources
The IR bit in the interrupt control register may be set to 1 (interrupt requested) when the interrupt source
changes. When using an interrupt, set the IR bit to 0 (no interrupt requested) after changing the interrupt source.
In addition, the changes of interrupt sources include all sources that change the interrupt sources assigned to
individual software interrupt numbers, polarities, and timing. Therefore, when a mode change of the peripheral
functions involves interrupt sources, edge polarities, and timing, Set the IR bit to 0 (no interrupt requested) after
the change. Refer to each peripheral function for the interrupts caused by the peripheral functions.
Figure 12.20 shows an Example of Procedure for Changing Interrupt Sources.
Figure 12.20 Example of Procedure for Changing Interrupt Sources
NOTES:
1. Execute the above settings individually. Do not execute two
or more settings at once (by one instruction).
2. To prevent interrupt requests from being generated, disable
the peripheral function before changing the interrupt
source. In this case, use the I flag if all maskable interrupts
can be disabled. If all maskable interrupts cannot be
disabled, use bits ILVL0 to ILVL2 of the interrupt whose
source is changed.
3. Refer to 12.6.5 Changing Interrupt Control Register
Contents for the instructions to be used and usage notes.
Interrupt source change
Disable interrupts
(2, 3)
Set the IR bit to 0 (interrupt not requested)
using the MOV instruction
(3)
Change interrupt source (including mode
of peripheral function)
Enable interrupts
(2, 3)
Change completed
IR bit: The interrupt control register bit of an
interrupt whose source is changed.
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