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LSSD In-Circuit Test on Cards with Limited Number of Pins

IP.com Disclosure Number: IPCOM000104080D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Baur, U: AUTHOR [+3]

Abstract

As the number of pins of complex C-MOS modules is limited, the module inputs (test pins/scan-ins) on cards are frequently combined. Although the card function is not affected, this is in contrast to LSSD design rules providing for each scan-in to be separately stimulatable. As a result, the LSSD vectors, which are normally obtained by disconnecting the pins during testing, can no longer be automatically generated so that relatively much manual work is needed.

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LSSD In-Circuit Test on Cards with Limited Number of Pins

      As the number of pins of complex C-MOS modules is limited, the
module inputs (test pins/scan-ins) on cards are frequently combined.
Although the card function is not affected, this is in contrast to
LSSD design rules providing for each scan-in to be separately
stimulatable.
 As a result, the LSSD vectors, which are normally obtained by
disconnecting the pins during testing, can no longer be automatically
generated so that relatively much manual work is needed.

      The errors occurring during card assembly are detected by an
in-circuit test.  As not all module inputs/outputs are available on
the card, a "needle bed" test is used.  By means of contact needles,
this tester is able to stimulate or measure the card pins P and thus
all module inputs/outputs substantially separately.

      By disconnecting the pins P on the in-circuit tester in the
test mode with the aid of a bus driver (Fig. 1) or resistors R (Fig.
2), test data is readily obtainable.  The manual work required is cut
down con siderably, time-consuming test data generation is eliminated
and the test quality is improved, while the data volume handled is
reduced.

      In the example of Fig. 1, the short-circuited inputs of the
modules are disconnected by switching off the bus driver DRV through
ENABLE.  As a result, the pins P at the output of driver DRV may be
separately stimulated.  In the example of Fig. 2, the resistors R...