82371AB Datasheet, PDF (191/284 Pages) Intel Corporation – PCI-TO-ISA / IDE XCELERATOR PIIX4

E
82371AB (PIIX4)
9.0. IDE CONTROLLER FUNCTIONAL DESCRIPTION
PIIX4 integrates a high performance interface from PCI to IDE. This interface is capable of accelerated PIO data
transfers as well as acting as a PCI Bus master on behalf of an IDE DMA slave device. PIIX4 provides an
interface for either primary and secondary IDE connectors or primary drive 0 and primary drive 1 IDE
connectors.
All the IDE data transfer command strobes, DMA request and grant signals, IORDY signal, address lines, and
data lines interface directly to PIIX4. Two full sets of signals are provided to enhance electrical isolation
capabilities.
Only PCI masters have access to the IDE port. ISA Bus masters cannot access the IDE I/O port addresses.
Memory targeted by the IDE interface acting as a PCI Bus master on behalf of IDE DMA slaves must reside on
PCI, usually main memory implemented by the host-to-PCI bridge.
The following descriptions of PIIX4 IDE signals may sometimes omit the Primary (P) or Secondary (S) prefix.
These descriptions apply to both sets of IDE signals. For example, references to IORDY apply to both PIORDY
and SIORDY.
9.1. IDE Signal Configuration
PIIX4 has two features that support a number of physical configuration options for system designers.
1. PIIX4 has two completely separate IDE channels. There are no shared signals between the two interfaces.
This improves signal timings and allows separate power management monitoring of both channels. Each
channels signals can be completely tri-stated or isolated. This allows individual power down of IDE devices
on separate channels. It can also be used to allow another device to drive the signal lines. This is useful for
Swap-Bay implementations where a system designer may have different types of devices inserted into the
bay (such as IDE device or floppy drive).
2. PIIX4 IDE channels can also be configured to support four devices in a Primary and Secondary channel
configuration or to support two devices in a Primary Drive 0 and Primary Drive 1 channel configuration. The
second configuration allows for the power management of individual devices and is very useful in a mobile
environment.
Figure 6 and Figure 7 show these configuration options.
PIIX4
IDE
Data and
Control
IDE
Data and
Control
Swap Bay Device
(IDE or Floppy)
Floppy
Data and
Control
PRELIMINARY
Figure 6. PIIX4 IDE Swap Bay Example
ide_swap
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4/9/97 2:23 PM PIIX4aDS
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