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M0A21/M0A23 Series
May 06, 2022
Page
262
of 746
Rev 1.02
M0
A21
/M
0
A
2
3
SE
RIES
TEC
H
NICAL
RE
FEREN
C
E
M
ANUAL
perform any operation transfer. Finishing each task will generate an interrupt to CPU if corresponding
PDMA interrupt bit is enabled and TBINTDIS (PDMA_DSCTn
_CTL[7]) bit is “0” (when finishing task and
TBINTDIS
bit is “0”, corresponding TDIFn (PDMA_TDSTS[4:0]) flag will be asserted and if this bit is “1”
TDIFn will not be active).
If channel 4 has been triggered, and the operation mode is in Scatter-Gather mode (OPMODE
(PDMA_DSCTn_CTL[1:0]) = 0x2), the hardware will load the real PDMA information task from the
address generated by adding PDMA_DSCTn_NEXT (link address) and PDMA_SCATBA (base
address) registers. For example, base address is 0x2000_0000 (only MSB 16 bits valid in
PDMA_SCATBA), the current link address is 0x0000_0100 (only LSB 16bits without last two bits [1:0]
valid in PDMA_DSCTn_NEXT), and then the next DSCT entry start address is 0x2000_0100.
DSCT4
DSCT3
.
.
.
DSCT_CTL
0
1
LSB 16 bits
without [1:0]
MSB 16 bits
SRAM
Load the information to
the channel 4 descriptor table
Current DSCT Entry
Next DSCT Entry
DSCT1
DSCT0
DSCT_NEXT
DSCT_DA
DSCT_SA
DSCT_NEXT
DSCT_DA
DSCT_SA
DSCT_CTL
PDMA_SCATBA
Descriptor table
Figure 6.6-4 Descriptor Table Link List Structure
The above link list table operation is DSCT state in Scatter-Gather Mode as shown in Figure 6.6-5.
When loading the information is finished, it will go to transfer state and start transfer by this information
automatically. However, if the next PDMA information is also set to Scatter-Gather mode, the hardware
will catch the next PDMA information block when the current task is finished. The Scatter-Gather mode
switches to basic mode when doing the next task. Then, the basic mode switches to Idle state when the
last task is finished.