
285
11.6 Hold Request Cancellation Requests
To execute high priority interrupt processing during CPU hold, the request of the hold
request issuing source must be canceled. The interrupt level used as the basis for
generating the cancellation request is set in the HRCL register.
s Basis for Generating Hold Request Cancellation Requests
When an interrupt source level that is greater than the interrupt level set in the HRCL register is
detected, a hold request cancellation request is generated.
If the HRCL register interrupt level is greater than the interrupt level after determining the
priority, a cancellation request is generated.
If the HRCL register interrupt level is less than or equal to the interrupt level after
determining the priority, no cancellation request is generated.
This cancellation request remains valid until the interrupt source used as the source for
generating cancellation requests is cleared. If cancellation of a hold request is requested during
DMA transfer, DMA transfer will not occur until the interrupt request is cleared; therefore, always
clear the corresponding interrupt source.
s Hold Request Cancellation Request Levels that Can be Set
The values that can be set in the HRCL register are the same as those of the ICR register. That
is, values between 10000B and 11111B are allowed.
When the HRCL register is set to 11111B, a cancellation request is generated for all interrupt
levels. When the HRCL register is set to 10000B, a cancellation request is generated for NMIs
only.
Table 11.6-1 "Settings of Interrupt Levels Used for Generating Hold Request Cancellation
Requests" lists the settings of the interrupt levels used for generating hold request cancellation
requests.
After a reset, the HRCL register is set to 11111 and DMA transfer is suppressed for all interrupt
levels.
Because DMA transfer cannot be performed when an interrupt occurs, set the HRCL register to
the required value.
Table 11.6-1 Settings of Interrupt Levels Used for Generating Hold Request Cancellation
Requests
HRCL register
Interrupt level used for generating cancellation requests
16
NMIs only
17
NMIs and interrupt level 16
18
NMIs and interrupt levels 16 and 17
31
NMIs and interrupt levels 16 to 30 (initial value)