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IDE Controller Registers (D31:F1)
9-6
82801AA and 82801AB Datasheet
9.1.14
IDE_TIM—IDE Timing Register (IDE—D31:F1)
Address Offsets:
Primary:
Secondary: 42
–
43h
0000h
40
–
41h
Attribute:
R/W
Default Value:
Size:
16 bits
This register controls the timings driven on the IDE cable for PIO and 8237 style DMA transfers.
The register also controls operation of the buffer for PIO transfers.
Bit
Description
15
IDE Decode Enable (IDE).
1 = Enables the ICH to decode the Command Blocks (1F0–1F7h for primary, 170–177h for
secondary) and Control Block (3F6h for primary and 376h for secondary).
NOTE:
Separate configuration bits are provided to individually disable the Primary or Secondary
decode (even if the IDE Decode Enable is set).
14
Drive 1 Timing Register Enable (SITRE).
0 = Use bits 13:12, 9:8 for both drive 0 and drive 1
1 = Use bits 13:12, 9:8 for drive 0, and use the Slave IDE Timing register for drive 1
13:12
IORDY Sample Point (ISP).
The setting of these bits determine the number of PCI clocks between
IDE IOR#/IOW# assertion and the first IORDY sample point.
00 = 5 clocks
01 = 4 clocks
10 = 3 clocks
11 = Reserved
11:10
Reserved.
9:8
Recovery Time (RCT).
The setting of these bits determines the minimum number of PCI clocks
between the last IORDY sample point and the IOR#/IOW# strobe of the next cycle.
00 = 4 clocks
01 = 3 clocks
10 = 2 clocks
11 = 1 clock
7
Drive 1 DMA Timing Enable (DTE1).
1 = Enable the fast timing mode for DMA transfers only for this drive. PIO transfers to the IDE data
port will run in compatible timing.
0 = Disable
6
Drive 1 Prefetch/Posting Enable (PPE1).
1 = Enable Prefetch and posting to the IDE data port for this drive.
0 = Disable
5
Drive 1 IORDY Sample Point Enable (IE1).
1 = Enable IORDY sampling for this drive.
0 = Disable IORDY sampling for this drive.
4
Drive 1 Fast Timing Bank (TIME1).
0 = Accesses to the data port will use compatible timings for this drive.
1 = When set and bit 14 cleared, accesses to the data port will use bits 13:12 for the IORDY sample
point, and bits 9:8 for the recovery time. When set and bit 14 set, accesses to the data port use
the IORDY sample point and recover time specified in the slave IDE timing register.
3
Drive 0 DMA Timing Enable (DTE0).
1 = Enable fast timing mode for DMA transfers only for this drive. PIO transfers to the IDE data port
run in compatible timing.
0 = Disable