SB82371 Intel Corporation, SB82371 Datasheet - Page 65

• Manufacturer Part Number: SB82371
• Description: 82371FB (PIIX) AND 82371SB (PIIX3) PCI ISA IDE XCELERATOR
• Manufacturer: Intel Corporation

2.5.1.8.
I/O Address:
Default Value:
Attribute:
This register determines the number of transfers to be performed. The actual number of transfers is one
more than the number programmed in the Current Byte/Word Count Register When the value in the
register is decremented from zero to FFFFh, a TC is generated. Autoinitialize can only occur when a
TC occurs. If it is not autoinitialized, this register has a count of FFFFh after TC.
For transfers to/from an 8-bit I/O, the Byte/Word count indicates the number of bytes to be transferred.
This applies to DMA channels 0-3. For transfers to/from a 16-bit I/O, with shifted address, the
Byte/Word count indicates the number of 16-bit words to be transferred. This applies to DMA channels
5-7.
2.5.1.9.
I/O Address:
Default Value:
Attribute:
This register works in conjunction with the Current Address Register. After an autoinitialization, this
register retains the original programmed value. Autoinitialize takes place after a TC.
15:0
7:0
Bit
Bit
DMA Low Page [23:16]. These bits represent address bits [23:16] of the 24-bit DMA address
Base and Current Byte/ Word Count. These bits represent the 16 byte/word count bits used
when counting down a DMA transfer.
DMA Base And Current Byte/Word Count Registers (Compatible Segment)
DMA Memory Low Page Registers
DMA Channel 0—001h
DMA Channel 1—003h
DMA Channel 2—005h
DMA Channel 3—007h
XXXXh (CPURST or Master Clear)
Read/Write
DMA Channel 0—087h
DMA Channel 1—083h
DMA Channel 2—081h
DMA Channel 3—082h
XXh (CPURST or Master Clear)
Read/Write
Description
Description
DMA Channel 4—0C2h
DMA Channel 5—0C6h
DMA Channel 6—0CAh
DMA Channel 7—0CEh
DMA Channel 5—08Bh
DMA Channel 6—089h
DMA Channel 7—08Ah
82371FB (PIIX) AND 82371SB (PIIX3)
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