Information

DMA request
DMA request
DMA request
Minor loopMinor loopMinor loop
Major loop
Current major
loop iteration
count (CITER)
3
2
1
Source or destination memory
Figure 21-101. Example of multiple loop iterations
The following figure lists the memory array terms and how the TCD settings interrelate.
xADDR: (Starting address)
xLAST: Number of bytes added to
current address after major loop
(typically used to loop back)
Minor loop
(NBYTES in
minor loop,
often the same
value as xSIZE)
Minor loop
Last minor loop
Offset (xOFF): number of bytes added to
current address after each transfer
(often the same value as xSIZE)
Each DMA source (S) and
destination (D) has its own:
Address (xADDR)
Size (xSIZE)
Offset (xOFF)
Modulo (xMOD)
Last Address Adjustment (xLAST)
where x = S or D
Peripheral queues typically
have size and offset equal
to NBYTES.
xSIZE: (size of one
data transfer)
Figure 21-102. Memory array terms
21.5.2 Programming errors
The eDMA 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 (ES[CPE]).
Chapter 21 Direct Memory Access Controller (eDMA)
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
Freescale Semiconductor, Inc. 385