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Interrupt Controller Modules
Freescale Semiconductor
17-5
17.2.2
Interrupt Mask Register (IMRH
n
, IMRL
n
)
The IMRH
n
and IMRL
n
registers are each 32 bits in size and provide a bit map for each interrupt to allow
the request to be disabled (1 equals disable the request, 0 equals enable the request). The IMRL register is
used for masking interrupt sources 0 to 31, while the IMRH register is used for masking interrupts 32 to
63. The IMR
n
is set to all ones by reset, disabling all interrupt requests. The IMR
n
can be read and written.
NOTE
A spurious interrupt may occur if an interrupt source is being masked in the
interrupt controller mask register (IMR) or a module’s interrupt mask
register while the interrupt mask in the status register (SR[I]) is set to a value
lower than the interrupt’s level. This is because by the time the status
register acknowledges this interrupt, the interrupt has been masked. A
spurious interrupt is generated because the CPU cannot determine the
interrupt source. To avoid this situation for interrupts sources with levels
1-6, first write a higher level interrupt mask to the status register, before
setting the mask in the IMR or the module’s interrupt mask register. After
the mask is set, return the interrupt mask in the status register to its previous
value. Because level 7 interrupts cannot be disabled in the status register
prior to masking, use of the IMR or module interrupt mask registers to
disable level 7 interrupts is not recommended.
Table 17-4. IPRL
n
Field Descriptions
Field
Description
31–0
INT
Interrupt Pending. Each bit corresponds to an interrupt source. The corresponding IMRL
n
bit determines whether an
interrupt condition can generate an interrupt. At every system clock, the IPRL
n
samples the signal generated by the
interrupting source. The corresponding IPRL
n
bit reflects the state of the interrupt signal even if the corresponding
IMRL
n
bit is set.
0 The corresponding interrupt source does not have an interrupt pending
1 The corresponding interrupt source has an interrupt pending
Address 0xFC04_8008 (IMRH0)
0xFC04_C008 (IMRH1)
Access: User read/write
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
R
INT_MASK
W
Reset 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Figure 17-3. Interrupt Mask Register High (IMRH
n
)
Содержание MCF54455
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