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M451
May. 4, 2018
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6.7.4 Basic Configuration
The peripheral direct memory access (PDMA) controller peripheral clock is enabled in
PDMACKEN (CLK_AHBCLK[1]).
6.7.5 Functional Description
The PDMA controller transfers data from one address to another without CPU intervention. For
M45xG/M45xE, the PDMA controller supports 12 independent channels, for M45xD/M45xC, the
PDMA controller supports 8 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 6.7-2 shows the diagram of descriptor table (DSCT) data structure.
Descriptor Table
DSCT11
DSCT10
DSCT1
DSCT0
DSCT_DA
DSCT_NEXT
Descriptor Table Entry Structure
0x0C
0x08
0x04
DSCT_SA
DSCT_CTL
0x00
0x00
DSCT2
DSCT3
DSCT5
DSCT4
DSCT6
DSCT7
DSCT8
DSCT9
0x10
0x20
0x30
0x40
0x50
0x60
0x70
0x80
0x90
0xA0
0xB0
Note: for
M45xC/M45xD
DSCT only from 0 to 7
Figure 6.7-2 Descriptor Table Entry Structure
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).
Channel Priority
6.7.5.1
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 6-11.