82801BA Datasheet, PDF (166/498 Pages) Intel Corporation – Intel 82801BA I/O Controller Hub 2 (ICH2) and Intel 82801BAM I/O Controller Hub 2 Mobile

Functional Description
Error Conditions
IDE devices are sector based mass storage devices. The drivers handle errors on a sector basis;
either a sector is transferred successfully or it is not. A sector is 512 bytes.
If the IDE device does not complete the transfer due to a hardware or software error, the command
will eventually be stopped by the driver setting Command Start bit to zero when the driver times
out the disk transaction. Information in the IDE device registers help isolate the cause of the
problem.
If the controller encounters an error while doing the bus master transfers it stops the transfer
(i.e., reset the Active bit in the Command register) and sets the Error bit in the Bus Master IDE
Status register. The controller does not generate an interrupt when this happens. The device driver
can use device specific information (PCI Configuration Space Status register and IDE Drive
Register) to determine what caused the error.
When a requested transfer does not complete properly, information in the IDE device registers
(Sector Count) can be used to determine how much of the transfer was completed and to construct
a new PRD table to complete the requested operation. In most cases the existing PRD table can be
used to complete the operation.
8237-Like Protocol
The 8237 mode DMA is similar in form to DMA used on the ISA bus. This mode uses pins
familiar to the ISA bus, namely a DMA Request, a DMA Acknowledge, and I/O read/write strobes.
These pins have similar characteristics to their ISA counterparts in terms of when data is valid
relative to strobe edges, and the polarity of the strobes, however the ICH2 does not use the 8237 for
this mode.
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82801BA ICH2 and 82801BAM ICH2-M Datasheet