10 May
2000
10 May
'00
12:36 p.m.
This wasn't the only clever part. They also
jammed instructions
into the 8080 to do fetches and stores. All they used were
a number of one shots, some glue logic and 3state buffers.
The first time I looked at how they did it, I was impressed.
I don't know if it was an original idea but it was clever.
Dwight
Only one instruction I think maybe jump and maybe nop. The reads and
writes to the pannel was more majik. The data bus displayed whatever
data was at the current location (or on the bus. To write a location all
you had to do was create a write pulse and gate the data onto the DO bus.
Most of the logic was single step(cycle) and single instruction Vs "run"
state.
I know this as I did a z80 machine with simpler STD like bus and made a cp
for it. It was mostly buffering the LEDS and gating the switches to the
bus and some simple timing logic (I used Clocked D and JK FFs rather than
oneshots). The WAIT/ line on the Z80 did all the work. The worst part of
building it was drilling/mounting/wiring 28 leds!
Allison