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NUC126
Aug. 08, 2018
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6.12.5.2 PDMA Operation Mode
The PDMA controller supports two operation modes including Basic mode and Scatter-Gather mode.
Basic Mode
Basic mode is used to perform one descriptor table transfer mode that shown as Figure 6.12-3. This
mode can be used to transfer data between memory and memory or peripherals and memory. PDMA
controller operation mode can be set from OPMODE (PDMA_DSCTn_CTL[1:0], n denotes PDMA
channel). PDMA will operation in idle mode by configured OPMODE bits to 1, the default setting is in
idle state (OPMODE (PDMA_DSCTn_CTL[1:0]) = 0) and recommend user configure the descriptor
table in idle state. If operation mode is not in idle state, user re-configure channel setting may make
some operation error.
User must enable the transfer channel CHENn (PDMA_CHCTL[4:0]) and fill the transfer count TXCNT
(PDMA_DSCTn_CTL[29:16])
register
and
select
transfer
width
TXWIDTH
(PDMA_DSCTn_CTL[13:12]),
destination
address
increment
size
DAINC
(PDMA_DSCTn_CTL[11:10]), source address increment size SAINC (PDMA_DSCTn_CTL[9:8]), burst
size BURSIZE (PDMA_DSCTn_CTL[6:4]) and transfer type TXTYPE (PDMA_DSCTn_CTL[2]), then
the PDMA controller will perform transfer operation in transfer state after receiving request signal.
Finishing this task will generate an interrupt to CPU if each PDMA interrupt bit INTENn
(PDMA_INTEN[4:0]) is enabled and the operation mode will be updated to idle state as shown in
Figure 6.12-4.
DSCT4
DSCT3
DSCT1
DSCT0
DSCT2
DSCT_CTL
SRAM or Peripheral register
Current DSCT4 Entry
DSCT_FIRST*
DSCT_DA
DSCT_SA
Source data
block
Destination data
block
Source address
Destination address
PDMA DSCT table
Transfer data
method controls
by DSCT_CTL
configuration
* : DSCT_FIRST value is ignored in basic mode
Figure 6.12-3 Descriptor Table Operation in Basic Mode
If software configures the operation mode to idle state, the PDMA controller will not perform any
transfer and then clear this operation request. Finishing this task will also generate an interrupt to CPU
if each PDMA interrupt bit is enabled.