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Browse Prior Art Database

Method to Test Data Bus Integrity

IP.com Disclosure Number: IPCOM000013900D
Original Publication Date: 2000-Dec-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 3 page(s) / 42K

Publishing Venue

IBM

Abstract

This is a test method using a unique data pattern (rolling bit pattern) to verify the integrity of a data bus in a computer. Although this test pattern was developed while working on an actual 16 bit ATA Hard Disk Drive bus problem, it could be applied to any size data bus within, or connected externally to a computer. The signal quality in a bi-directional data bus. whether on a board or through a cable, can be degraded because of: 1) The length of the traces 2) The impedance of the materials

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

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Method to Test Data Bus Integrity

This is a test method using a unique data pattern (rolling bit pattern) to verify the integrity of a data bus in a computer. Although this test pattern was developed while working on an actual 16 bit ATA Hard Disk Drive bus problem, it could be applied to any size data bus within, or connected externally to a computer.

The signal quality in a bi-directional data bus. whether on a board or through a cable, can be degraded because of:
1) The length of the traces
2) The impedance of the materials
3) Types of drivers and receivers
4) Crosstalk
5) Edge Rates
6) The number of signals driven high or low at the same time
7) Proximity of one data line to another data line, or control signal

Given the right conditions, it is possible to momentarily change the level of one data line when all remaining data lines are switch to a new level. If the single data line reaches the threshold level and remains there long enough, it may be clocked as a high instead of a low, or a low instead of a high.

This unique data pattern for a 16 bit data bus tests all combinations of setting the bus to one level, and then changing all but one of the data lines either high or low. This data can be written, then read from a device, and then compared for integrity.

This is the actual rolling 16 bit data pattern added to the IBM developed IX (IDE Exerciser) program to transfer data across the ATA bus. The ATA bus is bi-directional, so data may be transferred to, and from the device. The data transferred back can then be compared to the original data stored in a buffer.

This data is in the Intel format, so the 2 bytes in each word are reversed. word0 word1 word2 word3 word5 word6 word7 word8
00 00 fe ff 00 00 fd ff 00 00 fb ff 00 00 f7 ff
00 00 ef ff 00 00 df ff 00 00 bf ff 00 00 7f ff
00 00 ff fe 00 00 ff fd 00 00 ff fb 00 00 ff f7
00 00 ff ef 00 00 ff df 00 00 ff bf 00 00 ff 7f
fe ff 00 00 fd ff 00 00 fb ff 00 00 f7 ff 00 00
ef ff 00 00 df ff 00 00 bf ff 00 00 7f ff 00 00
ff fe 00 00 ff fd 00 00 ff fb 00 00 ff f7 00 00
ff ef 00 00 ff df 00 00 ff bf 00 00 ff 7f 00 00
00 00 f7 ff 00 00 fb ff 00 00 fd ff 00 00 fe ff
00 00 7f ff 00 00 bf ff 00 00 df ff 00 00 ef ff
00 00 ff f7 00 00 ff fb 00 00 ff fd 00 00 ff fe
00 00 ff 7f 00 00 ff bf 00 00 ff df 00 00 ff ef

1

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f7 ff 00 00 fb ff 00 00 fd ff 00 00 fe ff 00 00
7f ff 00 00 bf ff 00 00 df ff 00 00 ef ff 00 00
ff f7 00 00 ff fb 00 00 ff fd 00...