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Interrupt Controller Modules
Freescale Semiconductor
17-9
17.2.6
Clear Interrupt Mask Register (CIMR
n
)
The CIMR
n
register provides a simple mechanism to clear a given bit in the IMR
n
registers to enable the
corresponding interrupt request. The value written to the CIMR field causes the corresponding bit in the
IMR
n
register to be cleared. The CIMR
n
[CALL] bit provides a global clear function, forcing the entire
contents of IMR
n
to be cleared, thus enabling all interrupts. Reads of this register return all zeroes. This
register is provided so interrupt service routines can easily enable the given interrupt request without the
need to perform a read-modify-write sequence on the IMR
n
register.
In the event of a simultaneous write to the CIMR
n
and SIMR
n
, the SIMR
n
has priority and the resulting
function would be a set of the interrupt mask register.
17.2.7
Current Level Mask Register (CLMASK)
The CLMASK register is provided so the interrupt controller can optionally automatically manage
masking of interrupt requests based on the programmed priority level. If enabled by ICONFIG[EMASK]
bit being set, an interrupt acknowledge read cycle returns a vector number identifying the physical request
source, and the CLMASK register is loaded with the level number associated with the request. After the
CLMASK register is updated, then all interrupt requests with level numbers equal to or less than this value
are masked by the controller and are not allowed to cause the assertion of the interrupt signal to the
processor core. As the CLMASK register is updated during the IACK cycle read, the former value is saved
in the SLMASK register.
Typically, after a level-
n
interrupt request is managed, the service routine restores the saved level mask
value into the current level mask register to re-enable the lower priority requests. In addition, an interrupt
service routine can explicitly load this register with a lower priority value to query for any pending
interrupts via software interrupt acknowledge cycles.
Address: 0xFC04_801D (CIMR0)
0xFC04_C01D (CIMR1)
Access: User write-only
7
6
5
4
3
2
1
0
R
0
0
0
0
0
0
0
0
W
CALL
CIMR
Reset:
0
0
0
0
0
0
0
0
Figure 17-9. Clear Interrupt Mask Register (CIMR
n
)
Table 17-11. CIMR
n
Field Descriptions
Field
Description
7
Reserved, must be cleared.
6
CALL
Clear all bits in the IMR
n
register, enabling all interrupt requests.
0 Only set those bits specified in the CIMR field.
1 Clear all bits in IMR
n
register. The CIMR field is ignored.
5–0
CIMR
Clear the corresponding bit in the IMR
n
register, enabling the interrupt request.
Содержание MCF54455
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