North Star RAM-16-A Manual page 17

memory test program to verify correct operation of the
board. If you do not have a memory test program (such as
the TM command in the North star Monitor), then use the
program listed in Appendix 2.
If the RAM-16-A does not fail the memory test after several
hours of operation, then the board is operational and you
may skip the remaining checkout steps. If systematic data
or addressing errors are detected, then refer to the
schematic drawings to diagnose and correct the problem.
(The correspondence between addresses and RAM chips is given
in Appendix 3.) If the RAM-16-A does not operate at all,
then continue with step C3.
C3. Set the address switches labeled "2" and "3" on the DIP
switch (2nd and 3rd from the top) to the "ON" position. The
other six switches should be OFF. with the computer power
off, install ONLY the processor board and the RAM-16-A into
the computer motherboard. Turn on the power and depress and
hold down the computer reset switch so that no memory
requests are being made.
A. Check the following memory cycle request signals while the
computer reset switch is depressed:
Signal
Location Description
STORE/
4B pin 5
HIGH
INSTRUCTION-FETCH/ 4B pin 11 HIGH
FETCH/
4B pin 6
HIGH
RUNNING-REFRESH/
6C pin 6 HIGH
DEPOSIT-CY/
4B pin 4
HIGH
If the signals are not as listed then refer to the schematic
drawings and trace backwards to locate and correct the
problem.
B. WAITING-REFRESH cycles should occur approximately every 25
microseconds. In the following table, let T refer to the
period of PHI 2 in your computer (e.g., 250ns with a 4MHz
processor and 500ns with a 2MHz processor). Check the
following signals while the computer reset switch is
depressed:
Signal Location Description
WRF 2A pin 3 AC, (+T,2Sus)
WAITING-REFRESH/
Ie pin 12 AC, (-T,2Sus)
CYCLE-START 4B pin
8
AC, (+T,2Sus)
delay tapTI SA pin 12
AC,
(+T,25us)
delay tap T2 5A pin 4 AC, (+T,25us)
delay tap T3
SA pin 10 AC, (+T,2Sus)
delay tap T4 SA pin 6 AC, (+T,25us)
North Star 16K RAM Board 16