AT&T 6300 Service Manual page 253

DIAGNOSTICS
Addressing Test: This test writes into each memory location
its address. The memory is then checked to verify the addresses.
This test is then repeated, writing the complement of the address
into each memory location.
Fixed Pattern Test: This test writes to each memory location
the current test pattern and immediately verifies the pattern. The
test cycles through all of the memory 24 times, using a different
pattern each time. The 24 patterns in hexadecimal format are:
AAAA, FFFF, 0000, 5555, 0101, 0202, 0404, 0808, 1010, 2020, 4040,
8080, FEFE, FDFD, FBFB, F7F7, EFEF, DFDF, BFBF, 7F7F,
FFOO, DOFF, AA55, and 55AA.
Marching Pattern Test: The same 24 patterns used in the
fixed pattern test are used in this test. The memory is first filled
with the first pattern. Starting at the beginning of memory, the
pattern is read and verified, and then the complement of the
pattern is written into the cell and verified. The test then goes to
the next cell and repeats the same process until the end-of-memory
is reached. When the end-of-memory is reached, the test starts
backwards verifying the pattern, complementing it, storing it, and
verifying it. This is repeated for each cell until the beginning
location is reached. This process is repeated for all 24 patterns.
All of the memory is written and read 96 times in this test.
Moving Inversion Test: This test uses a complex algorithm in
that a field of zero bits is inverted and then reinverted again with
each pass. This process is repeated using address steps, which
with each pass are multiplied by two. This test is run first with a
forward sequence and then a backward sequence. The main
characteristics of this algorithm are that each write is written
between two read actions, and that the addresses are generated in
different increments and directions.
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