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Data Integrity and Error Handling
6-20 Intel® 460GX Chipset Software Developer’s Manual
6.11 PCI Integrity
The PCI bus provides a single even-parity bit (PAR) that covers the AD[31:0] and C/BE#[3:0]
lines. The agent that drives the AD[31:0] lines is responsible for driving PAR. Any undefined
signals must still be driven to a valid logic level and included in the parity calculation.
6.11.1 PCI Bus Monitoring
When the PXB is not the PCI bus master, it will still check the address parity for all PCI address
phases. If a parity error is detected and the Parity Error Response is enabled in the PCI Command
(PCICMD) register, the event is logged in the Parity Error Detected bit in the PCI Status
(PCISTS) register. If the PCICMD register’s SERR# Enable bit (SERRE) is set, SERR# will
also be asserted. When the PXB asserts SERR#, the PCISTS register’s Signalled System Error bit
(SSE) is also set.
Note that the expected settings for the GX system are: SERRE=1, PERRE=1, ERRCMD[3]=1, and
ERRCMD[4]=1. ERRCMD[6:5] are to be programmed as each OEM, operating system or system
user desires in order to enable SERR reporting of data parity errors. For data which has bad parity
and is received from the PCI bus, the PXB will forward this up the Expander bus as if there were no
parity error, so that ERRCMD[5] may need to be set for sufficient error containment, since PERR#
asserted to the card will not prevent the data which had a parity error from being placed in memory
6.11.2 PXB as Master
6.11.2.1 Master Abort
If the PXB initiates a PCI transaction and no target responds, the PXB will terminate the
transaction with a master-abort. The PXB will wait five PCI clocks after asserting FRAME# for a
target to respond with DEVSEL#. If no target responds, the PXB will perform a master abort to
terminate the cycle on the PCI bus. Special Cycle commands, which are broadcast to all PCI
targets, will always be terminated with master abort. Therefore master-aborts during Special Cycle
commands are not considered errors, and are never logged or reported.
When the PXB performs a master abort, if the command was not a Special cycle, it will log the
event by setting the PCISTS register’s Received Master Abort (RMA) bit. The PXB then has two
options for generating a response.
Detected as PCI Target
PCI Par-err on
Address from Card
PXB Accept address as sent
and process as if parity
were good.
Conditionally assert
SERR#.
PCISTS[PE], PCISTS
[SSE], ERRSTS[2]
Nothing
SERRE
PCI Par-err on
Data for an IB Write
PXB Set Status. Drive
PERR#. Pass data with
good parity to Expander.
ERRSTS [5] Nothing
PERR# Asserted
by Card
card Optionally turned to
SERR# by PXB.
ERRSTS[6],
PCISTS[DPE]
Nothing
Table 6-1. Error Cases (Cont’d)
Error
Chip
Detecting
System
Action
Status
Register
Log
Register
Qualifier