Browse Prior Art Database

Improved Diagnostic for Logic Fault Locator

IP.com Disclosure Number: IPCOM000120013D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 63K

Publishing Venue

IBM

Related People

Aichelmann Jr, FJ: AUTHOR [+2]

Abstract

A method is proposed for loading of specific portions of a long shift register latch (SRL) scan ring to save system time and provide unique diagnostic capability. The long SRL scan ring may cross many logic function boundaries and several chips. This is especially true for memory cards where address, control, data, etc., functions are all contained in a large scan ring (Fig. 1). For some diagnostic purposes, loading only the SRLs of a particular function or section with special patterns may be required. This function or section can be clocked in normal (functional) fashion to observe the effect on the attached logic at the primary outputs or another set of SRLs.

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Improved Diagnostic for Logic Fault Locator

      A method is proposed for loading of specific portions of
a long shift register latch (SRL) scan ring to save system time and
provide unique diagnostic capability.  The long SRL scan ring may
cross many logic function boundaries and several chips.  This is
especially true for memory cards where address, control, data, etc.,
functions are all contained in a large scan ring (Fig. 1).  For some
diagnostic purposes, loading only the SRLs of a particular function
or section with special patterns may be required. This function or
section can be clocked in normal (functional) fashion to observe the
effect on the attached logic at the primary outputs or another set of
SRLs. Additionally, if several groups of SRLs in a scan ring perform
a similar function (such as data buffers), they may now be loaded
with the same data at the same time for testing.  This method will
reduce diagnostic time at system power on or IPL.

      Fig. 2 shows the modified SRL which would be in front of each
of the SRL groups of interest.  Fig. 3 shows how the groups may be
positioned in a scan ring.

      Operation is as follows:
           1.  With 'A' and 'B' clocks "on" flush O's
               through the entire scan ring.
           2.  Toggle all "Bypass Mode Selects," thus
               loading "O's" into 'L' and allowing normal
               scan path operation.
   ...