13 Oct
2007
13 Oct
'07
5:32 p.m.
On 10/13/07, Roy J. Tellason <rtellason at verizon.net> wrote:
On Saturday 13 October 2007 15:40, dwight elvey
wrote:
Oh, heck, I'd forgotten about PMOS stuff altogether! :-)
Hmm... PMOS... I know that there are fundamental composition and
voltage differences between NMOS, PMOS, CMOS, HMOS, etc... What makes
it not-compatible with TTL (unlike CMOS, which is easy to interface to
TTL)?
>
4008/9? First I've heard of these at all.
These were but interface chips that took the pmos levels and convertered
then to TTL levels to use with standard RAM, ROM, EPROM and I/O. From time to time, I consider building a small 4004
board - nothing
more complicated than a digital clock, but my lack of examples to
study in detail always slows me down. I've read over various
datasheets, but not recently enough to really recall any specifics. I
happen to have a couple of 4004s already - one plastic, one ceramic
package, but they came from devices that I didn't have schematics for
(one digital kitchen scale, one early barcode reader), and don't have
the original PCBs from to study.
I can't say that a modern 4004 project would be practical, but it sure
would be neat to watch. I know there were some older bi-polar 4-bit
PROMs that should still be programmable with 25-year-old programmers,
but I suppose that it's just easy enough to use modern 8-bit devices
and ignore 4 of the bits.
-ethan