On 03/05/2012 03:41 PM, Eric Smith wrote:
Ethan Dicks wrote about the COSMAC Elf:
To guess, I know of one common issue with
hand-made 1802 designs -
the 4016 and 4066 are not 100% interchangable. They have different
switch response characteristics. ISTR the older designs used 4016
switches which are harder to find now than 4066 switches.
It's certainly true
that the 4016 and 4066 have differences in their
characteristics. However, in the simple way in which it is used in
the Elf, I can't see how it would make any difference. I can't say
that I've actually tried it, though.
I have no difference.
If not that,
then the other issue to investigate is to ensure that
the input button is debounced
Yes, that is quite important.
that and also making sure all the wires go where they are supposed to.
I've built many of the COSMAC ELFs over the years and still have my wire
wrapped original, a
QUEST PCB version and a few more wire wrapped variants. I made a version
of the ELF on S100.
I also have the EELF and ELF2000. It was a simple and very
non-critical CPU to build up and make work.
Of the old CPUs I still play with and use the Z80 (Z180, Z280) are most
used, 8085 the next, 8048/51,
1802, and the 6100(pdp8). Of all the 1802 is the most interesting as
it's not unlike the PDP-8 in that its
simple to the extreme yet still useful.
Allison