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M0A21/M0A23 Series
May 06, 2022
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Rev 1.02
M0
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SE
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TEC
H
NICAL
RE
FEREN
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ANUAL
6.6.5
Functional Description
The PDMA controller transfers data from one address to another without CPU intervention. The PDMA
controller supports 5 independent channels and serves only one channel at one time, as the result,
PDMA controller supports two level channel priorities: fixed and round-robin priority, PDMA controller
serves channel in order from highest to lowest priority channel. The PDMA controller supports two
operation modes: Basic mode and Scatter-gather mode. Basic mode is used to perform one descriptor
table transfer. Scatter-gather mode has more entries for each PDMA channel, and thus the PDMA
controller supports sophisticated transfer through the entries. The descriptor table entry data structure
contains many transfer information including the transfer source address, transfer destination address,
transfer count, burst size, transfer type and operation mode. Figure 6.6-2 shows the diagram of
descriptor table (DSCT) data structure.
Descriptor Table
DSCT4
DSCT_DA
DSCT_NEXT
Descriptor Table Entry Structure
0x0C
0x08
0x04
DSCT_SA
DSCT_CTL
0x00
0x40
DSCT3
DSCT0
DSCT1
DSCT2
0x00
0x10
0x20
0x30
Figure 6.6-2 Descriptor Table Entry Structure
The PDMA controller also supports single and burst transfer type and the request source can be from
software or peripheral request, transfer between memory to memory using software request. A single
transfer means that software or peripheral is ready to transfer one data (every data needs one request),
and the burst transfer means that software or peripherals will transfer multiple data (multiple data only
need one request).
6.6.5.1
Channel Priority
The PDMA controller supports two level channel priorities including fixed and round-robin priority. The
fixed priority channel has higher priority than round-robin priority channel. If multiple channels are set
as fixed or round-robin priority, the higher channel will have higher priority. The priority order is listed in
Table 6.6-1.
PDMA_PRISET
Channel Number
Priority Setting
Arbitration Priority In Descending
Order
1
4
Channel4, Fixed Priority
Highest
1
3
Channel3, Fixed Priority
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1
0
Channel0, Fixed Priority
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