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LPC/FWH Interface Configuration
11-16 Intel® 460GX Chipset Software Developer’s Manual
11.2.1.2 Dcm–Dma Channel Mode Register (I/O)
I/O Address: Channels 0-3=0Bh; Channels 4-7=0D6h
Default Value: Bits[7:2]=0; Bits[1:0]=undefined (CPURST or Master Clear)
Attribute: Write Only
Each channel has a 6-bit DMA Channel Mode Register. The Channel Mode Registers provide
control over DMA transfer type, transfer mode, address increment/decrement, and auto-
initialization.
11.2.1.3 Dr–Dma Request Register (I/O)
I/O Address: Channels 0-3–09h; Channels 4-7–0D2h
Default Value: Bits[1:0]=undefined; Bits[7:2]=0 (CPURST or Master Clear)
Attribute: Write Only
The Request Register is used by software to initiate a DMA request. The DMA responds to the
software request as though DREQx is asserted. These requests are non-maskable and subject to
prioritization by the priority encoder network. For a software request, the channel must be in Block
Mode. The Request Register status for DMA1 and DMA2 is output on bits [7:4] of a Status
Register read.
Bit Description
7:6 DMA Transfer Mode. Each DMA channel can be programmed in one of four different modes:
Bits[7:6] Transfer Mode
00 Demand Mode
01 Single Mode
10 Block Mode
11 I Cascade Mode
5 Address Increment/Decrement Select. 0=Increment; 1=Decrement.
4 Auto-initialize Enable. 1=Enable; 0=Disable.
3:2 DMA Transfer Type. When Bits [7:6]=11, the transfer type bits are irrelevant.
Bits[3:2] Transfer Type
00 Verify transfer
01 Write transfer
10 Read transfer
11 I Illegal
1:0 DMA Channel Select. Bits [1:0] select the DMA Channel Mode Register written to by bits [7:2].
Bits[1:0] Channel
00 Channel 0 (4)
01 Channel 1 (5)
10 Channel 2 (6)
11 Channel 3 (7)
Bit Description
7:3 Reserved. Must be 0
2 DMA Channel Service Request. 0=Resets the individual software DMA channel request bit.
1=Sets the request bit. Generation of a TC also sets this bit to 0.
1:0 DMA Channel Select. Bits [1:0] select the DMA channel mode register to program with bit 2.
Bits[1:0] Channel
00 Channel 0
01 Channel 1 (5)
10 Channel 2 (6)
11 Channel 3 (7)