Browse Prior Art Database

Error Detection Card

IP.com Disclosure Number: IPCOM000119603D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Dodge, MR: AUTHOR

Abstract

A difficult task in analyzing diskette-drive read problems is to be able to see what happened when the error occurred. One method is to have a hardware-generated signal at the instant the error happens. This design provides a signal pulse at the error that can be used to trigger a logic analyzer. The logic analyzer can then record which logic events took place near the error.

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Error Detection Card

      A difficult task in analyzing diskette-drive read
problems is to be able to see what happened when the error occurred.
One method is to have a hardware-generated signal at the instant the
error happens.  This design provides a signal pulse at the error that
can be used to trigger a logic analyzer.  The logic analyzer can then
record which logic events took place near the error.

      Data to be read from a diskette is sent in serial form from the
drive to the floppy-disk control module.  The control module puts the
data in byte form and sends it to the computer on the parallel bus.
This logic samples each byte of data and, if not correct, generates
an error signal pulse.

      First, each sector in the diskette (to be read) must be written
with a repeating byte pattern, such as ABABAB, etc. Then the switches
in this logic must be set to this pattern, AB.  As a read operation
takes place, the actual data on the bus is compared to the switches.
If a miscompare occurs, a signal pulse is generated.  This pulse will
be within 1-byte time of when the data is picked up by the diskette
drive head on the media.

      A common pattern used in drive/media testing is a tri-nibble,
such as DB6DB6, etc.  To accommodate this pattern, three switches are
provided in the design.  They are set to DB, B6, and 6D,
respectively.  When a repeating byte pattern is used, each switch is
set the same, such as AB, AB, and AB.

      This logic ...