LPC Interface Bridge Registers (D31:F0)
9-24
Intel
82801BA ICH2 Datasheet
9.2.1
DMABASE_CA—DMA Base and Current Address Registers
I/O Address:
Ch. #0 = 00h; Ch. #1 = 02h
Ch. #2 = 04h; Ch. #3 = 06h
Ch. #5 = C4h Ch. #6 = C8h
Ch. #7 = CCh;
Undef
No
Attribute:
Size:
RO
16-bit (per channel),
but accessed in two 8-bit
quantities
Default Value:
Lockable:
Power Well:
Core
CEh
CFh
Channel 7 DMA Base & Current Count Register
Undefined
R/W
D0h
D1h
Channel 4–7 DMA Command Register
Undefined
WO
Channel 4–7 DMA Status Register
Undefined
RO
D4h
D5h
Channel 4–7 DMA Write Single Mask Register
000001XXb
WO
D6h
D7h
Channel 4–7 DMA Channel Mode Register
000000XXb
WO
D8h
D9h
Channel 4–7 DMA Clear Byte Pointer Register
Undefined
WO
DAh
DBh
Channel 4–7 DMA Master Clear Register
Undefined
WO
DCh
DDh
Channel 4–7 DMA Clear Mask Register
Undefined
WO
DEh
DFh
Channel 4–7 DMA Write All Mask Register
0Fh
R/W
Table 9-2. DMA Registers (Continued)
Port
Alias
Register Name/Function
Default
Type
Bit
Description
15:0
Base and Current Address
—R/W.
This register determines the address for the transfers to be
performed. The address specified points to two separate registers. On writes, the value is stored in
the
Base Address
register and copied to the
Current Address
register. On reads, the value is returned
from the
Current Address
register.
The address increments/decrements in the Current Address register after each transfer, depending
on the mode of the transfer. If the channel is in auto-initialize mode, the Current Address register will
be reloaded from the Base Address register after a terminal count is generated.
For transfers to/from a 16-bit slave (channels 5–7), the address is shifted left one bit location. Bit 15
will be shifted out. Therefore, if bit 15 was a 1, it will be lost.
The register is accessed in 8 bit quantities. The byte is pointed to by the current byte pointer flip/flop.
Before accessing an address register, the byte pointer flip/flop should be cleared to ensure that the
low byte is accessed first.
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