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82801AA and 82801AB Datasheet
8-25
LPC Interface Bridge Registers (D31:F0)
8.2.6
DMA_WRSMSK—DMA Write Single Mask Register
I/O Address:
Ch. #0
–
3 = 0Ah;
Ch. #4
–
7 = D4h
0000 01xx
No
Attribute:
Size:
Power Well:
WO
8 bits
Core
Default Value:
Lockable:
8.2.7
DMACH_MODE—DMA Channel Mode Register
I/O Address:
Ch. #0
–
3 = 0Bh;
Ch. #4
–
7 = D6h
0000 00xx
No
Attribute:
Size:
Power Well:
WO
8 bits
Core
Default Value:
Lockable:
Bit
Description
7:3
Reserved. Must be 0.
2
Channel Mask Select.
1 = Disable DREQ for the selected channel.
0 = Enable DREQ for the selected channel. The channel is selected through bits [1:0]. Therefore,
only one channel can be masked / unmasked at a time.
1:0
DMA Channel Select.
These bits select the DMA Channel Mode Register to program.
00 = Channel 0 (4)
01 = Channel 1 (5)
10 = Channel 2 (6)
11 = Channel 3 (7)
Bit
Description
7:6
DMA Transfer Mode.
Each DMA channel can be programmed in one of four different modes:
00 = Demand mode
01 = Single mode
10 = Reserved
11 = Cascade mode
5
Address Increment/Decrement Select.
This bit controls address increment/decrement during DMA
transfers.
0 = Address increment. (default after part reset or Master Clear)
1 = address decrement.
4
Autoinitialize Enable.
1 = DMA restores the Base Address and Count registers to the current registers following a terminal
count (TC).
0 = Autoinitialize feature is disabled and DMA transfers terminate on a terminal count. A part reset or
Master Clear disables autoinitialization.
3:2
DMA Transfer Type.
These bits represent the direction of the DMA transfer. When the channel is
programmed for cascade mode, (bits[7:6] = “11”) the transfer type is irrelevant.
00 = Verify–No I/O or memory strobes generated
01 = Write–Data transferred from the I/O devices to memory
10 = Read–Data transferred from memory to the I/O device
11 = Illegal
1:0
DMA Channel Select.
These bits select the DMA Channel Mode Register that will be written by bits
[7:2].
00 = Channel 0 (4)
01 = Channel 1 (5)
10 = Channel 2 (6)
11 = Channel 3 (7)