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MPC563XM Reference Manual, Rev. 1
140
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
Table 7-16. DMA Error (DMAERRH, DMAERRL) Field Descriptions
7.3.1.15
DMA Channel n Priority (DCHPRIn), n = 0,..., {15,31,63}
When the fixed-priority channel arbitration mode is enabled (DMACR[ERCA] = 0), the contents of these
registers define the unique priorities associated with each channel within a group. The channel priorities
are evaluated by numeric value, i.e., 0 is the lowest priority, 1 is the next higher priority, then 2, 3, etc.
Software must program the channel priorities with unique values, otherwise a configuration error will be
reported. The range of the priority value is limited to the values of 0 through 15. When read, the GRPPRI
bits of the DCHPRIn register reflect the current priority level of the group of channels in which the
corresponding channel resides. GRPPRI bits are not affected by writes to the DCHPRIn registers. The
group priority is assigned in the DMACR. See
Channel preemption is enabled on a per channel basis by setting the ECP bit in the DCHPRIn register.
Channel preemption allows the executing channel’s data transfers to be temporarily suspended in favor of
starting a higher priority channel. Once the preempting channel has completed all of its minor loop data
transfers, the preempted channel is restored and resumes execution. After the restored channel completes
one read/write sequence, it is again eligible for preemption. If any higher priority channel is requesting
service, the restored channel will be suspended and the higher priority channel will be serviced. Nested
preemption (attempting to preempt a preempting channel) is not supported. Once a preempting channel
begins execution, it cannot be preempted. Preemption is only available when fixed arbitration is selected
for both group and channel arbitration modes. See
for the DCHPRIn
definition.
Figure 7-16. DMA Channel n Priority (DCHPRIn) Register
Table 7-17. DMA Channel n Priority (DCHPRIn) Field Descriptions
Name
Description
Value
ERRn,
n = 0,... 15
n = 0,... 31
n = 0,... 63
DMA Error n
0 An error in channel n has not occurred.
1 An error in channel n has occurred.
Register address: DMA_ 0x100 + n
7
6
5
4
3
2
1
0
R
ECP
0
GRPPRI[1:0]
CHPRI[3:0]
W
RESET:
0
*
*
*
*
*
*
RESET:
0
0
*
*
*
*
*
*
= Unimplemented,
*
= defaults to channel number (n) after reset
Name
Description
Value
ECP
Enable Channel Preemption
0 Channel n cannot be suspended by a higher
priority channel’s service request.
1 Channel n can be temporarily suspended by the
service request of a higher priority channel.