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Method to correct PCI parity errors produced by a faulty PCI agent

IP.com Disclosure Number: IPCOM000099011D
Original Publication Date: 2005-Mar-09
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 22K

Publishing Venue

IBM

Abstract

This article shows how to solve a problem where a faulty PCI agent produces bad parity data during a PCI configuration read cycle. The basic concept of this invention is to intercept and correct the PAR bit during a configuration read of the faulty device. The advantage to using this invention is that it allows you to use the faulty device without having to disable parity detection for the entire PCI bus. Parity detection at the device does need to be disabled since the device won't see valid parity data during writes.

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Method to correct PCI parity errors produced by a faulty PCI agent

     This article shows how to solve a problem where a faulty PCI agent produces bad parity data during a PCI configuration read cycle. The basic concept of this invention is to intercept and correct the PAR bit during a configuration read of the faulty device. The advantage to using this invention is that it allows you to use the faulty device without having to disable parity detection for the entire PCI bus. Parity detection at the device does need to be disabled since the device won't see valid parity data during writes.

     The correction of PCI parity is accomplished by having a CPLD (or equivalent logic) monitor the PCI bus and the IDSEL input of the faulty device. When the CPLD detects a configuration read cycle to the device, it will calculate the correct parity for the read data generated by the device and drive that parity data at the appropriate time on the PCI bus. Since this approach requires the PAR bit from the faulty device to be disconnected from the PCI bus, it will be necessary to disable parity detection at the device. See figure for reference.

Parity Detection Disabled

CPLD

Parity

Logic

AD Bus w/PAR

IDSEL

Faulty

 PCI Agent

 PCI Agent

PCI Bus w/o PAR

 PCI Agent

Compatibility PCI Bus

 PCI Agent

Parity Detection Enabled

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