🚀 go-pugleaf

> Re Small Count Microprocessor Systems

The Intel 8031 microprocessor is one that I've used and works fine.  It's
got 128 bytes of internal ram, a serial port, two timers (one of which can
act as a baud rate clock for the serial port) and one to one and a half 8
bit parallel ports all for NZ$5 (probably about US$3).  To run it needs an
EPROM and an address latch (usually 74LS373).  

The processor is fast with most of the instructions completing in one
microsecond.  It can have up to 64K of EPROM and 64K of external RAM (at
the same time).

The architecture is a bit warped, which is fine if you're using assembler
for small projects or a compiler for big ones (but don't try to write a
compiler for it - I did and it's tortuously painful - irregularities
EVERYWHERE).  

To get at the external RAM you have to move the data into the accumulator
through a single index register, modify it and put it back, which tends
to slow things down a bit.  

An eprom version (8751) was quite expensive last time I looked around
(US$30 I think) but is available if you need a single chip solution
(sounds like a saleman :-).  There is also a version with built in
floating point BASIC and EPROM BURNING routines and needs only a terminal.
Steve Ciarcia did an article in BYTE on these (8052-basic)


If you need to modify large data structures (which must necessarily be in
external ram) one of the Motorola processors is probably a better bet
(I've also build and programmed Motorola 6802 & 6809 systems) ,otherwise
the 8031 is cheap, fast and widely available.  

Cheers
Giovanni

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