µDMA Channel Control Structure Registers
624
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Micro Direct Memory Access (µDMA)
Table 8-16. DMACHCTL Register Field Descriptions (continued)
Bit
Field
Type
Reset
Description
25-24
SRCSIZE
R/W
X
Source Data Size
This field configures the source item data size.
DSTSIZE must be the same as SRCSIZE.
0x0 = Byte; 8-bit data size.
0x1 = Half-word; 16-bit data size.
0x2 = Word; 32-bit data size.
0x3 = Reserved
23-22
RESERVED
R
0x0
21
DSTPROT0
R/W
0x0
Destination Privilege Access
This bit controls the privilege access protection for destination data
writes.
For AES, DES, or SHA accesses, this bit must be set to 1.
0 = The access is nonprivileged.
1 = The access is privileged.
20-19
RESERVED
R
X
18
SRCPROT0
R/W
0x0
Source Privilege Access
This bit controls the privilege access protection for source data
reads.
For AES, DES, or SHA accesses, this bit must be set to 1.
0 = The access is nonprivileged.
1 = The access is privileged.
17-14
ARBSIZE
R/W
X
Arbitration Size
This field configures the number of transfers that can occur before
the µDMA controller re-arbitrates.
The possible arbitration rate configurations represent powers of 2
and are shown below.
0x0 = 1 TransferArbitrates after each µDMA transfer
0x1 = 2 Transfers
0x2 = 4 Transfers
0x3 = 8 Transfers
0x4 = 16 Transfers
0x5 = 32 Transfers
0x6 = 64 Transfers
0x7 = 128 Transfers
0x8 = 256 Transfers
0x9 = 512 Transfers
0xA-0xF = 1024 Transfers. In this configuration, no arbitration occurs
during the µDMA transfer because the maximum transfer size is
1024.
13-4
XFERSIZE
R/W
X
Transfer Size (minus 1)
This field configures the total number of items to transfer. The value
of this field is 1 less than the number to transfer (value 0 means
transfer 1 item). The maximum value for this 10-bit field is 1023
which represents a transfer size of 1024 items.
The transfer size is the number of items, not the number of bytes. If
the data size is 32 bits, then this value is the number of 32-bit words
to transfer.
The µDMA controller updates this field immediately before entering
the arbitration process, so it contains the number of outstanding
items that is necessary to complete the µDMA cycle.
3
NXTUSEBURST
R/W
X
Next Useburst
This field controls whether the Useburst SET[n] bit is automatically
set for the last transfer of a peripheral scatter-gather operation.
Normally, for the last transfer, if the number of remaining items to
transfer is less than the arbitration size, the µDMA controller uses
single transfers to complete the transaction.
If this bit is set, then the controller uses a burst transfer to complete
the last transfer.