NXP Semiconductors MPC5605BK, Справочное руководство

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Chapter 16 Enhanced Direct Memory Access (eDMA)
MPC5606BK Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 285
Figure 16-22. Example of multiple loop iterations
Figure 16-23 lists the memory array terms and how the TCD settings interrelate.
Figure 16-23. Memory array terms
16.5.2 DMA programming errors
The DMA performs various tests on the transfer control descriptor to verify consistency in the descriptor
data. Most programming errors are reported on a per-channel basis with the exception of channel-priority
error, or EDMA_ESR[CPE].
For all error types other than channel-priority errors, the channel number causing the error is recorded in
the EDMA_ESR. If the error source is not removed before the next activation of the problem channel, the
error will be detected and recorded again.
DMA request
Minor loop 3
Current major loop
iteration count
(CITER)
Example memory array
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•
•
DMA request
Minor loop 2
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•
•
DMA request
Minor loop 1
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Major loop
xADDR:
(Starting address)
xSIZE:
(Size of one data
Minor loop
(NBYTES in
minor loop, often
the same value
as xSIZE)
Offset (xOFF): Number of
bytes added to current
address after each transfer
(Often the same value
as xSIZE)
•
Minor loop
Each DMA source (S) and
destination (D) has its own:
• Address (xADDR)
• Size (xSIZE)
• Offset (xOFF)
xLAST: Number of bytes
added to current address
Peripheral queues typically
have size and offset
equal to NBYTES
•
•
after major loop
(typically used to
loop back)
transfer)
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•
•
•
•
•
Last minor loop
• Modulo (xMOD)
• Last address adjustment
(xLAST) where x = S or D
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