LM3S1607 Luminary Micro, Inc, LM3S1607 Datasheet - Page 202

• Manufacturer Part Number: LM3S1607
• Description: Lm3s1607 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

Micro Direct Memory Access (μDMA)
202
Bit/Field
17:14
13:4
3
NXTUSEBURST
XFERSIZE
ARBSIZE
Name
Type
R/W
R/W
R/W
Reset
-
-
-
Preliminary
Description
Arbitration Size
Sets the number of DMA transfers that can occur before the controller
re-arbitrates. The possible arbitration rate settings represent powers of
2 and are shown below.
Transfer Size (minus 1)
Sets 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 controller updates this field immediately prior to it entering the
arbitration process, so it contains the number of outstanding DMA items
that are necessary to complete the DMA cycle.
Next Useburst
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 controller will use single transfers to complete
the transaction. If this bit is set, then the controller will only use a burst
transfer to complete the last transfer.
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA-0xF
Description
1 Transfer
Arbitrates after each DMA transfer.
2 Transfers
4 Transfers
8 Transfers
16 Transfers
32 Transfers
64 Transfers
128 Transfers
256 Transfers
512 Transfers
1024 Transfers
This means that no arbitration occurs during the DMA transfer
because the maximum transfer size is 1024.
June 02, 2008