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Diagnostic Error Check/Wrap As a Means of On-Line Error Detection

IP.com Disclosure Number: IPCOM000042818D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Ellis, JJ: AUTHOR [+2]

Abstract

Early detection of module failure and the provision for component isolation is an important aspect of hardware development. Registers and memories may be written and read-back for test purposes. But complex data paths internal to a display adapter are much more difficult to test. This is especially true if the test is performed by a local microprocessor with limited resources. Typically, this verification is performed with each power on and when specifically requested by the display operator. A "generic" way to check a piece of logic, is to apply mode data and input patterns and to check the output of the logic against a predetermined value (Fig. 1). This results in the number of checks equaling the number of modes times the amount of data generated per operation. This has been referred to as "Diagnostic Wrap".

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Diagnostic Error Check/Wrap As a Means of On-Line Error Detection

Early detection of module failure and the provision for component isolation is an important aspect of hardware development. Registers and memories may be written and read-back for test purposes. But complex data paths internal to a display adapter are much more difficult to test. This is especially true if the test is performed by a local microprocessor with limited resources. Typically, this verification is performed with each power on and when specifically requested by the display operator. A "generic" way to check a piece of logic, is to apply mode data and input patterns and to check the output of the logic against a predetermined value (Fig. 1). This results in the number of checks equaling the number of modes times the amount of data generated per operation. This has been referred to as "Diagnostic Wrap". The advantage of this mode is that all functional logic paths can be checked. The disadvantage is the volume of data generated. A great deal of memory is needed to store the expected pattern for each test of the system adapter for a large screen display (almost 1500 bytes for an 80-character row) and time for a byte by byte comparison by the associated microprocessor must be allocated. A preferred alternative is referred to as Diagnostic Error Check mode. This mode uses a minimal amount of logic to perform the checking of data internal to the display adapter (gas panel adapter). As in the generic approach, a mode and variable input patterns are provided. But data reduction is performed to the extent that a single PASS/FAIL bit is available for microprocessor interrogation (Fig. 2). This is made possible be selecting the mode...