Intel
82801BA ICH2 Datasheet
2-5
Signal Description
PDA[2:0],
SDA[2:0]
O
Primary and Secondary IDE Device Address:
These output signals are
connected to the corresponding signals on the primary or secondary IDE
connectors. They are used to indicate which byte in either the ATA command
block or control block is being addressed.
PDD[15:0],
SDD[15:0]
I/O
Primary and Secondary IDE Device Data:
These signals directly drive the
corresponding signals on the primary or secondary IDE connector. There is a
weak internal pull-down resistor on PDD[7] and SDD[7].
PDDREQ,
SDDREQ
I
Primary and Secondary IDE Device DMA Request:
These input signals are
directly driven from the DRQ signals on the primary or secondary IDE connector.
It is asserted by the IDE device to request a data transfer, and used in
conjunction with the PCI bus master IDE function. They are not associated with
any AT-compatible DMA channel. There is a weak internal pull-down resistor on
these signals.
PDDACK#,
SDDACK#
O
Primary and Secondary IDE Device DMA Acknowledge:
These signals
directly drive the DAK# signals on the primary and secondary IDE connectors.
Each signal is asserted by the ICH2 to indicate to the IDE DMA slave devices that
a given data transfer cycle (assertion of DIOR# or DIOW#) is a DMA data transfer
cycle. This signal is used in conjunction with the PCI bus master IDE function and
are not associated with any AT-compatible DMA channel.
PDIOR#
SDIOR#
O
Primary and Secondary Disk I/O Read (PIO and Non-Ultra DMA):
This is the
command to the IDE device that it may drive data on the PDD or SDD lines. Data
is latched by the ICH2 on the deassertion edge of PDIOR# or SDIOR#. The IDE
device is selected either by the ATA register file chip selects (PDCS1# or
SDCS1#, PDCS3# or SDCS3#) and the PDA or SDA lines, or the IDE DMA
acknowledge (PDDAK# or SDDAK#).
Primary and Secondary Disk Write Strobe (Ultra DMA Writes to Disk):
This is
the data write strobe for writes to disk. When writing to disk, ICH2 drives valid
data on rising and falling edges of PDWSTB or SDWSTB.
Primary and Secondary Disk DMA Ready (Ultra DMA Reads from Disk):
This
is the DMA ready for reads from disk. When reading from disk, ICH2 deasserts
PRDMARDY# or SRDMARDY# to pause burst data transfers.
PDIOW#
SDIOW#
O
Primary and Secondary Disk I/O Write (PIO and Non-Ultra DMA):
This is the
command to the IDE device that it may latch data from the PDD or SDD lines.
Data is latched by the IDE device on the deassertion edge of PDIOW# or
SDIOW#. The IDE device is selected either by the ATA register file chip selects
(PDCS1# or SDCS1#, PDCS3# or SDCS3#) and the PDA or SDA lines, or the
IDE DMA acknowledge (PDDAK# or SDDAK#).
Primary and Secondary Disk Stop (Ultra DMA):
ICH2 asserts this signal to
terminate a burst.
PIORDY
SIORDY
I
Primary and Secondary I/O Channel Ready (PIO):
This signal keeps the strobe
active (PDIOR# or SDIOR# on reads, PDIOW# or SDIOW# on writes) longer than
the minimum width. It adds wait states to PIO transfers.
Primary and Secondary Disk Read Strobe (Ultra DMA Reads from Disk)
:
When reading from disk, ICH2 latches data on rising and falling edges of this
signal from the disk.
Primary and Secondary Disk DMA Ready (Ultra DMA Writes to Disk)
: When
writing to disk, this is deasserted by the disk to pause burst data transfers.
Table 2-6. IDE Interface Signals (Continued)
Name
Type
Description
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