Donn Steward CPUville 8-bit Instruction Manual - Page 12

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Testing and Using the Register Display

Plug the ICs into the sockets, being careful not to bend under any pins. A bent-under pin can look like a
properly inserted pin from the top.
The register display can be tested by putting +5V and ground onto pins 1 and 50 of the display
connector, respectively. Because the inputs to the buffers are not connected in this condition, they will
assume a high level, and the LEDs will light. Then, you can ground the pins on the display connector
one-by-one. The corresponding LED should go out. Pins 7, 9, 11, 13, 14 and 15 of the front panel
connector can be tested in the same way. The clock selector switches connected to pins 2, 4 and 6 can
be tested for continuity with pin 12 of the 16-pin front panel connector when closed. The switch
connected to pin 8 can be tested for continuity with pin 10 when closed. The pushbuttons can be tested
for grounding pins 1, 3, and 5 when closed (pressed).
To use the display, remove the control board from the processor stack and connect the 50-conductor
ribbon cable to the display connector on the main board. Then replace the control board, being careful
to line up the receptacle on the bottom of the control board with the control connector header on the
main board. Turn off the switches on the control board, because you will be using the switches on the
display board to control the computer. Place 0.5 inch male/female standoffs on the threads coming
through the mounting holes on the control board. Then connect the 50-conductor cable to the display
connector on the display board. Line up the front panel connector on the bottom of the display board
with the 16-pin header on the control board. If lined up properly, the mounting holes will be in line
with the standoffs on the control board. Put the female standoffs (nuts) onto the threads. The display
board should show activity when the computer is powered up.
The switches and pushbuttons on the display board correspond to the switches and buttons on the
control board, and are used the same way.
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