Radio Shack 26-3801 Service Manual page 147

ROM CRC Check
After pressing
the
'1'
key
at the menu, the program will display
'CRC =' and pause
for
a
few seconds before displaying
the
ROM
CRC.
Once the test
is complete, press any key
to
return
to
the menu.
The CRC generated
by this test
is a
simple
16
bit sum of all the
bytes
of
ROM (from 0000 hex through
7FFF hex).
The current ROM CRC value
is
A2D4
New Checksums can
be listed here:
RAM Check
After selecting
option '2'
from the menu,
the
program will clear
the
screen and display
the
RAM
test as they are executed. There
are three
tests that are performed,
the first
of
which
is
the 00 Fill.
This
test fills the section
of
RAM being tested with zeros and then read
the
RAM
to
make
sure that the zeros were written.
The second
test
is
the FF
Fill and operates
in the
same manner, except that
it
uses FF
hex to fill memory instead
of zero.
The last test
is the
Rotating
fill. This tests
fills RAM with
a
sequential pattern
from 01-FF hex until all RAM
that
is
being tested
is
filled and
the
checks
to see
that the same sequence
is
read back
from
the RAM.
It
makes
255
passes, each pass beginning the sequence
with
a
different value.
(The first pass will begin the
sequence with
1,2,3,4,5...; The second pass will begin
the sequence with
2,3,4,5,6..., etc.
) .
The following table shows
the
amount
of
time that each RAM Check will
take for each RAM size
available
for Model 100.
Program 8K
16K 24K 32K
MEMLO
2
. 1
min.
4
.
2
min.
6
.
3
min
9
.
4
min
MEMHI
3
min.
3
min.
3
min.
3
min.
All times are approximate