Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ames!lll-winken!scooter!neoucom!wtm
From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: sci.electronics
Subject: Re: 1802
Summary: 1802 is CMOS, but that is about all it has going for it
Message-ID: <1874@neoucom.UUCP>
Date: 16 Jan 90 01:28:30 GMT
References: <3218@uceng.UC.EDU> <914@xroads.UUCP>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 36


I agree.  The 1802 is a rather brain-dead microprocessor.  There
are some very odd machinations that the programmer must put up with
for calling and returning from subroutines on this beast.

Of historical note is that the RCA Cosmac 1802 was virtually the
first, if not *the* first CMOS process mircoprocessor.  This made
the 1802 a very attractive candidate for space-borne electronic
control systems, military electronics, and  harsh enviornments with
high electromagnetic interference levels.  I worked for a certain
government agency in 1979 - 1980, and the 1802 was the only
microprocessor that we could use because the 1802 was the only MPU
chip that was fully qualified for space avionics.  Yuck!  We were
looking forward to seeing CMOS versions of the Z-80 and 8080 that
were then on drawing boards.

Thre are a lot better chips around to use for learning projects.
Ironically, the 1802 is rather expensive if you can find any stock,
becuase the 1802 never became terribly popular.  Once CMOS versions
of popular consumer chips became available, the 1802 with its
quirky instruction set became less attractive.

The Z-80 and the ubiquitous 6502 are available for just a couple of
dollars and are quite easy to assemble into simple systems.  There
are a lot of books tageted at the two aforementioned chips.  The
65C02 is nice to work with because the desing is fully static and
does not have any maximum durations on clock states.

Steve Ciarcia has several build-it-yourself type books.  Joseph
Carr also worte, "Interface Your Microcomputer to Virtually
Anthing", which is a good starter text.



Bill
wtm@neoucom.edu  (...!lll-winken!scooter!neouocm!wtm)