Initialization and Configuration
1202
SPRUHE8E – October 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
M3 Micro Direct Memory Access ( µDMA)
channel control structure for this transfer.
3. Set bit 30 of the DMA Channel Useburst Clear (DMAUSEBURSTCLR) register to allow the µDMA
controller to respond to single and burst requests.
4. Set bit 30 of the DMA Channel Request Mask Clear (DMAREQMASKCLR) register to allow the µDMA
controller to recognize requests for this channel.
16.4.2.2 Configure the Channel Control Structure
After configuring the channel attributes, the channel control structure must be configured.
This example transfers 256 words from one memory buffer to another. Channel 30 is used for a software
transfer, and the control structure for channel 30 is at offset 0x1E0 of the channel control table. The
channel control structure for channel 30 is located at the offsets shown in
Table 16-7. Channel Control Structure Offsets for Channel 30
Offset
Description
Control Table Base + 0x1E0
Channel 30 Source End Pointer
Control Table Base + 0x1E4
Channel 30 Destination End Pointer
Control Table Base + 0x1E8
Channel 30 Control Word
16.4.2.2.1 Configure the Source and Destination
Now set the source and destination end pointers to the last address for the transfer (inclusive).
1. Program the source end pointer at offset 0x1E0 to the address of the source 0x3FC.
2. Program the destination end pointer at offset 0x1E4 to the address of the destination 0x3FC.
The control word at offset 0x1E8 must be programmed according to
.
Table 16-8. Channel Control Word Configuration for Memory Transfer Example
Field in DMACHCTL
Bits
Value
Description
DSTINC
31:30
2
32-bit destination address
increment
DSTSIZE
29:28
2
32-bit destination data size
SRCINC
27:26
2
32-bit source address
increment
SRCSIZE
25:24
2
32-bit source data size
Reserved
23:18
0
Reserved
ARBSIZE
17:14
3
Arbitrates after 8 transfers
XFERSIZE
13:4
255
Transfer 256 items
NXTUSEBURST
3
0
N/A for this transfer type
XFERMODE
2:0
2
Use Auto-request transfer
mode
16.4.2.3 Start the Transfer
The channel is configured and is now ready to start.
1. Enable the channel by setting bit 30 of the DMA Channel Enable Set (DMAENASET) register.
2. Issue a transfer request by setting bit 30 of the DMA Channel Software Request (DMASWREQ)
register.
The µDMA transfer begins. If the interrupt is enabled, then the processor is notified by interrupt when the
transfer is complete. If needed, the status can be checked by reading bit 30 of the DMAENASET register.
This bit is automatically cleared when the transfer is complete. The status can also be checked by reading
the XFERMODE field of the channel control word at offset 0x1E8. This field is automatically cleared at the
end of the transfer.