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EXERCISE 26 : IC IDENTIFIER (PRE-SEARCH CHECKS)
ACTION
Ensure BDO LOW is attached to TP1. Place the SOIC clip on U13. Take note of the settings
and device type we have selected. Press STARTon the IC tester. Check the device for signs of
activity.
DESCRIPTION
Prior to using the IC Identifier the condition on the IC being searched should be initially
checked for activity and good connection. If it is a good IC, the IC Identifier will identify it
and any ICs which are functionally and pin compatible (providing that the IC is in the
SYSTEM 8 test library). If there are changing signals on the device then these need to be
removed to allow the proper tests to be carried out.
COMMENTS
If prior IC tests have been carried out in circuit you will have a better understanding of the
activity you might expect on the PCB and it will help in isolating the device being searched
from Clocks and other signals. It is important to check that any open circuits are not related
to bad clip connection.
EXERCISE 27 : IC IDENTIFIER
ACTION
Ensure clip still on U13 74LS244. Note the settings for IC Identifier. Press START.
DESCRIPTION
The IC Identifier instrument is designed to identify ICs where the number is missing or
cannot be read, or the function of the IC is not known. This will only work if the IC is
functional. If the IC is faulty, its functionality cannot be identified and therefore it will not be
recognised. If it is a good IC, the IC Identifier will identify it and any ICs which are
functionally and pin compatible (providing that the IC is in the SYSTEM 8 test library).
COMMENTS
The IC Identifier is ideal for identifying ICs with missing markings. It will also display other
ICs in the library, which have the same functionality and pin-out as the IC being identified. It
is often the case when identifying an IC that several ICs are listed, all having the same
function. Depending on the way the IC is connected, however, there may sometimes be
equivalents listed which are not directly compatible. This is caused by the AUTOMATIC
CIRCUIT COMPENSATION function that will sometimes cause one IC to PASS the test for
another depending on the external connections.
If an IC requires certain board conditions in order to PASS the test, for example, BDO or
ground clip connections, those same conditions will be required in order to identify the IC. For
this reason, it is good practise to always disable clocks, always reset microprocessors, and
always use the ground clip when using the IC Identifier
The alternatives given are equivalent in the circuit configuration found. Care should be taken
to ensure that other parameters, such as speed and drive, are taken into account before
replacement.
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