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Initialization and Configuration
614
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Micro Direct Memory Access (µDMA)
8.4.2 Configuring a Memory-to-Memory Transfer
µDMA channel 30 is dedicated for software-initiated transfers. However, any channel can be used for
software-initiated, memory-to-memory transfer if the associated peripheral is not being used.
8.4.2.1
Configure the Channel Attributes
First, configure the channel attributes:
1. Program bit 30 of the DMA Channel Priority Set (DMAPRIOSET) or DMA Channel Priority Clear
(DMAPRIOCLR) registers to set the channel to high priority or default priority.
2. Set bit 30 of the DMA Channel Primary Alternate Clear (DMAALTCLR) register to select the primary
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.
8.4.2.2
Configure the Channel Control Structure
Now 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 8-6. 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
8.4.2.2.1 Configure the Source and Destination
The source and destination end pointers must be set 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
(1)
The value of this bit must be 1 (privileged) for AES, DES, or SHA accesses.
Table 8-7. 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
23:22
0
Reserved
DSTPROT0
(1)
21
0
Privileged access protection for destination data writes
Reserved
20:19
0
Reserved
SRCPROT0
(1)
18
0
Privileged access protection for source data reads
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