GD32F20x User Manual
233
Full_Data Mode
In Full_Data mode, the transfer size of source and destination must not be equal and the
transfer size of source
must be 32-bit. If the transfer size of destination is 16-bit, each DMA
transfer is achieved with one source operation followed by two destination operations. If the
transfer size of destination is 8-bit, four destination operations are needed to complete one
DMA transfer. Suppose DMA_CHxCNT is 2, and both PNAGA and MNAGA are set. The DMA
transfer operations for each combination of PWIDTH and MWIDTH are shown in the following
table.
Table 12-2. DMA transfer operations (Full_Data Mode)
Transfer size
Transfer operations
Source
Destination
Source
Destination
32 bits
16 bits
1: Read B3B2B1B0[31:0] @0x0
1: Write B1B0[16:0] @0x0
2: Write B3B2[16:0] @0x2
2: Read B7B6B5B4[31:0] @0x4
1: Write B5B4[16:0] @0x4
2: Write B7B6[16:0] @0x6
32 bits
8 bits
1: Read B3B2B1B0[31:0] @0x0
1: Write B0[7:0] @0x0
2: Write B1[7:0] @0x1
3: Write B2[7:0] @0x2
4: Write B3[7:0] @0x3
2: Read B7B6B5B4[31:0] @0x4
1: Write B4[7:0] @0x4
2: Wirte B5[7:0] @0x5
3: Write B6[7:0] @0x6
4: Write B7[7:0] @0x7
NOTE
:
The Full_Data transfer mode is only available for the channel 5 of DMA1.
12.4.2.
Peripheral handshake
To ensure a well-organized and efficient data transfer, a handshake mechanism is introduced
between the DMA and peripherals, including a request signal and a acknowledge signal:
–
Request signal asserted by peripheral to DMA controller, indicating that the peripheral is
ready to transmit or receive data
–
Acknowledge signal responded by DMA to peripheral, indicating that the DMA controller
has initiated an AHB command to access the peripheral
Figure 12-2. Handshake mechanism
shows how the handshake mechanism works between
the DMA controller and peripherals.
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