Changing the Connection Test Fault Coverage

Introduction

The XJTAG connection test is an automated interconnect test which checks for shorts, opens, stuck high and stuck low errors on a circuit board. Some circuit boards have cross-talk or similar issues, which do not affect the normal running of the board, but are picked up by the XJTAG connection test. To handle such boards, there are three debug options which can be used to change how the connection test runs.

Project File Preamble

There is an optional section in the XJEase project file preamble which can be used to modify the way that the connection test is run. This section can be used to run a special debug mode version of the connection test.

Alternatively, it can be used to handle boards with cross-talk and similar issues, as described below.

Syntax

CONNTEST
TEST := CONNTEST;
MAX_NETS := INTEGER;
INDIRECT := [ ALL | CONNECTION ];
ONE_WAY := [ TRUE | FALSE ];
END;

CONNTEST is the normal connection test. It can take up to three parameters.

MAX_NETS
This limits the number of nets that may change value simultaneously, helping to prevent ground bounce during the test.
INDIRECT
This controls how many nets will be tested for indirect shorts (shorts via a resistor) during the connection test. Nets which contain components in the CONNECTION LIST are always tested for indirect shorts. Set INDIRECT := ALL; to test all nets for indirect shorts.
ONE_WAY
This controls whether nets will be tested for one-way indirect shorts (via a buffer and a resistor) during the connection test. By default, such errors are ignored, as floating nets may mimic this type of error.

Example

CONNTEST
TEST := CONNTEST;
MAX_NETS := 20;
INDIRECT := ALL;
END;

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