Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!decwrl!mejac!orchard.la.locus.com!fafnir.la.locus.com!dana From: dana@locus.com (Dana H. Myers) Newsgroups: sci.electronics Subject: Re: Minimum requirements for CPU Message-ID: <1991Jan16.005401.2832865@locus.com> Date: 16 Jan 91 00:54:01 GMT References: <12610@hubcap.clemson.edu> <50574@sequent.UUCP> Organization: Locus Computing Corporation, Inglewood, CA Lines: 64 In article <50574@sequent.UUCP> jimp@crg1.UUCP (James Pilcher) writes: >In article <12610@hubcap.clemson.edu> tdaniel@hubcap.clemson.edu (tod daniels) writes: >> >>I've just started a project which will require some sort of control device >>which must be capable of collecting data and storing it, then manipulating >>it. >> >>I would like to use an 8085, and I'd like to know what are the bare essentials >>for running this chip?? I only need a small amount of RAM, some ROM, a way >>to read brief ASCII data, and a way to poll about four different on/off >>switches. Would I be better of to find a chip with on-chip ROM, RAM, and I/O?? >>Or should I go for the 8085 with as many chips as are necessary to make this >>project work?? > >it seems to me you need an intel 8051. this has 128 bytes of onboard >"registers", is available with eprom, and has 24 bits of i/o ports, >all on one chip. it would give you a much lower chip count, and is >a well proven chip. Jim is correct. An 8051, or maybe a Motorola part, would solve your problem more easily, from what I can tell, than the more general 8085. In the Intel MCS-51 family, though, there are many variants. The later variants are quite neat, with high function capture/compare timers and A/D converters and stuff like that. The barebones chip, without an on-chip ROM (which would be useless for you since you need to write your own s/w) is an 8031. A CMOS part is available also, and is known as the 80C31. The 8032 has an additional timer on the chip with enhanced baud rate generation, also the '32 has an additional 128 bytes of RAM for a total of 256 bytes. The MCS-51 family uses distinct code and data address spaces, up to 64k of each. There are instructions to read code space as data (such as looking up a table or other constant). There is no 80C32 from Intel; other vendors may offer such a part. Intel offers the 80C51FA, which is like a CMOS 8032 but has the neat 'Programmable Counter Array', which provides capture/compare + watchdog + timers/interrupts. Neat chip, about $10 in small lots. The 80C31 is about $4 in small lots. If you can get a deal on surplus, programmed 8051 or 8052 chips, these work equally well with external memory (see below). There are 32 bits of I/O on the chip; if you use an EPROM or ROM part (once again, this may not be practical) you can use all 32 bits. When using the chip with external program/data memory, you need to hang an octal latch (one of the following: 74LS373, 74LS573, 74HC373 or 74HC573 - the '573 is the same as a '373 with a better pin-out) off of Port 0 and use Port 2 as the upper 8 bits of address; effectively reducing you to 16 bits of I/O. If you use any of the extended functions, like the on-chip serial port or external interrupts, you give up additional I/O pins (they're shared). Call up Intel and order the Automotive Handbook or the Embedded Controller Handbook (2 volume set). The Automotive book is cheaper than the 2 volume Embedded Controller set, and has all the salient data. Signetics also sells '51 family parts. I've use MCS-51 parts for lots of things; they're pretty good. The MCS-96 is REALLY neat, but probably overkill for most little things. (Though an 80C196KA with A/D converter makes a really good lab controller... you can measure voltages, period, time, frequency, you name it, and the chip is easy to write code for). -- /* * Dana H. Myers KK6JQ | Views expressed here are * * (213) 337-5136 | mine and do not necessarily * * dana@locus.com | reflect those of my employer *