PIIX datasheet(51/122 Pages) INTEL

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82371FB (PIIX) AND 82371SB (PIIX3)

2.3.10.

IDETIM—IDE TIMING REGISTER (Function 1)

Address Offset:

Primary Channel=40–41h; Secondary Channel=42–43h

Default Value:

0000h

Attribute:

Read / Write Only

This register controls the PIIX's IDE interface and selects the timing characteristics of the PCI Local Bus IDE

cycle. Note that primary and secondary denotations distiguish between the cables and the 0/1 denotations

distiguish between master (0) and slave (1).

Bit

Description

IDE Decode Enable (IDE). 1=Enable; 0=Disable. When enabled, I/O transactions on PCI

targeting the IDE ATA register blocks (command block and control block) are positively

decoded on PCI and driven on the IDE interface. When disabled, these accesses are

subtractively decoded to ISA.

PIIX: Reserved.

PIIX3: Slave IDE Timing Register Enable (SITRE). 1=Enable SIDETIM Register. 0=Disable

(default) SIDETIM Register. When enabled, the ISP and RTC values can be programmed

uniquely for each master through the fields in this register and these values can be

programmed for each slave through the SIDETIM Register. When disabled, the ISP and RTC

values programmed in this register apply to both master and slave drives on each channel.

13:12

IORDY Sample Point (ISP). This field selects the number of clocks between DIOx#

assertion and the first IORDY sample point.

Bits[13:12]

Number Of Clocks

11:10

Reserved

9:8

Recovery Time (RTC). This field selects the minimum number of clocks between the last

IORDY# sample point and the DIOx# strobe of the next cycle.

Bits[9:8]

Number Of Clocks

DMA Timing Enable Only (DTE1). When DTE1=1, fast timing mode is enabled for DMA

data transfers for drive 1. Note that PIO transfers to the IDE data port still run in compatible

timing.

Prefetch and Posting Enable (PPE1). When PPE1=1, prefetch and posting to the IDE data

port is enabled for drive 1.

IORDY Sample Point Enable Drive Select 1 (IE1). When IE1=0, IORDY sampling is

disabled for Drive 1. The internal IORDY signal is forced asserted guaranteeing that IORDY

is sampled asserted at the first sample point as specified by the ISP field in this register.

When IE1=1 and the currently selected drive (via a copy of bit 4 of 1x6h) is Drive 0, all

accesses to the enabled I/O address range sample IORDY. The IORDY sample point is

specified by the ISP field in this register.

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