12 Dec
2005
12 Dec
'05
10:05 p.m.
Gooijen, Henk wrote:
Using the pdp8/e design fron panel for the 6809 is
possible, but ...
there are only 15 Address LEDs (12 plus 3 for EMA), and the other row is
12 LEDs, so the upper 4 would not be used. The rotary knob could be used
to display A or B (or DP or CC) but to display X, Y, U, SP, PC you need
16 LEDs. There are just 12 switches, and you could use the SW switch as
the 13th, but still, to enter a 16-bit address would be cumbersome.
So, the pdp8/e panel is not the best choice, but the implementation
-hardware wise- is always possible. Software is what makes it 'tick' :-)
and I am sure that's "piece of cake" for you, Dave.
As you all know by now I am building a 9/18 bit cpu. My front panel
will be limited to
9 data switches and a address page switch. This lets me access 000.nnn
and 777.nnn
memory on address load. Since I plan only to use the swr for short
programs on page zero
and have a bootstrap rom and I/O on the last page this more than ample
for me.
A similar restricted front panel may be possible as well for the 6809 as
data is byte orientated.
Ben alias woodelf