Array Testing with Minimal Hardware

Array Testing with Minimal Hardware

       Disclosed is a method for testing embedded arrays on a
chip with minimal dedicated test hardware.

      In order to deliver a defect-free chip, all embedded arrays
must be fully tested.  The most time efficient way of accomplishing
this is to test all arrays in parallel.  While parallel testing may
be the fastest method, it also requires that a large area of the chip
be dedicated to test hardware. Each array would require a dedicated
test input latch, as well as a dedicated test output latch.

      Instead of having dedicated test hardware for each array, a lot
of that hardware can be shared by multiple arrays.  A single test
input latch can be used to source multiple arrays.  A single test
output latch can be used to observe the outputs of multiple arrays.

      This is accomplished by decoding the upper address bits to
control the muxing of array outputs to a single test latch as shown
in the figure.