
82801AA and 82801AB Datasheet
2-5
Signal Description
2.5
Low Pin Count (LPC) Interface
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 is
asserted by the ICH to indicate to 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# /
(PDWSTB /
PRDMARDY#)
SDIOR# /
(SDWSTB /
SRDMARDY#)
O
Primary and Secondary Disk I/O Read (PIO and Non-Ultra ATA):
This is the
command to the IDE device that it may drive data onto the PDD or SDD lines. Data
is latched by the ICH 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 SDCS1#) and the PDA or SDA lines, or the IDE DMA acknowledge
(PDDAK# or SDDAK#).
Primary and Secondary Disk Write Strobe (Ultra ATA Writes to Disk):
This is
the data write strobe for writes to disk. When writing to disk, ICH drives valid data
on rising and falling edges of PDWSTB or SDWSTB.
Primary and Secondary Disk DMA Ready (Ultra ATA Reads from Disk):
This is
the DMA ready for reads from disk. When reading from disk, ICH deasserts
PRDMARDY# or SRDMARDY# to pause burst data transfers.
PDIOW# /
(PDSTOP)
SDIOW# /
(SDSTOP)
O
Primary and Secondary Disk I/O Write (PIO and Non-Ultra ATA):
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 ATA):
ICH asserts this signal to
terminate a burst.
PIORDY /
(PDRSTB /
PWDMARDY#)
SIORDY /
(SDRSTB /
SWDMARDY#)
I
Primary and Secondary I/O Channel Ready (PIO):
This signal will keep 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 ATA Reads from Disk):
When
reading from disk, ICH latches data on rising and falling edges of this signal from
the disk.
Primary and Secondary Disk DMA Ready (Ultra ATA Writes to Disk):
When
writing to disk, this is deasserted by the disk to pause burst data transfers.
Table 2-5. LPC Interface Signals
Name
Type
Description
LAD[3:0]
/
FWH[3:0]
I/O
LPC Multiplexed Command, Address, Data:
Internal pull-ups are provided.
LFRAME#
/
FWH[4]
O
LPC Frame:
Indicates the start of an LPC cycle, or an abort.
LDRQ[0]#
I
LPC Serial DMA/Master Request Inputs:
Used to request DMA or bus master
access. Typically connected to external Super I/O device.
LDRQ[1]#
/
GPIO[8]
I
LPC Serial DMA/Master Request Inputs:
Second DMA or bus master request. If
LDRQ[1]# is not needed, it can be used as a General Purpose Input.
Table 2-4. IDE Interface Signals (Sheet 2 of 2)
Name
Type
Description