Path: utzoo!attcan!uunet!ncrlnk!ncrcae!hubcap!gatech!gitpyr!byron From: byron@pyr.gatech.EDU (Byron A Jeff) Newsgroups: comp.sys.m68k Subject: Re: Simple M68000 design wanted Keywords: M68000 Message-ID: <7533@pyr.gatech.EDU> Date: 11 Mar 89 17:00:29 GMT References: <520@qantel.UUCP> <25975@cornell.UUCP> <13631@jumbo.dec.com> Reply-To: byron@pyr.UUCP (Byron A Jeff) Distribution: na Organization: Georgia Institute of Technology Lines: 120 In article <13631@jumbo.dec.com> ehs@jumbo.dec.com (Ed Satterthwaite) writes: -> In article <25975@cornell.UUCP>, rbrown@svax.cs.cornell.edu (Russell Brown) -> writes: -> In article <520@qantel.UUCP> jerry@qantel.UUCP (Jerry Gardner) writes: -> -> >I am looking for a simple design for an M68000 system that I can adapt for -> -> There's a pretty good design for an M68000 single-board system in the book by -> Wilcox (I can't remember the name of the book, but it's red ... - -The title is "68000 Microcomputer Systems: Designing and Troubleshooting" -by Alan D. Wilcox. - -Another book of possible interest is "Microprocessor-based Design" by -Michael Slater, which I can also recommend as a general reference. - -Either of these books will cost you more than a handful of 68000s. An -alternative is to mix and match from some Motorola application notes, e.g. - -AN867 A High Performance MC68000L12 System with No Wait States -AN896A Serial I/O, Timer and Interface Capabilities of the MC68901 - Multifunction Peripheral - [illustrated by a simple 68008 system using DRAM] -AN897 MC68008 Minimum Configuration System [also DRAM] - -Have you priced memory recently? The bus and memory width you save going -from a 68000 to 68008 ought to pay for the processor chip. Better yet, -have you thought about the 68HC11 or something similar? The impression I got from the original posting was that he alreay had a 68008 and wanted to experiment. Not all toys need to be big and go fast ;-) If he doesn't have a 68008 he should get one. Double busses for a first project is not the best move. It does cost less than a 32K static ram. AN897 (of which I have a copy) is a bit too complicated for the beginning user. When it was designed the only static ram that existed was 2K and cost a bunch. With a 120ns 32K static at $15 apiece (quoted from a JDR add in the Feb. Computer Shopper) memory for a test system won't break you. If one is seriously interested in building 68K stuff then the M68000KIT for Motorla is the way to go. You get 3 processors (a 68008, 68000, 68010), a 68091 MFP, a 68681 Duart, a 68440 DMA controller, and a couple or three other chips. Plus the latest copies of all the data book and application notes. I got mine on a $68 special. I think they normally run the mid $80 range. If I just wanted to play around I would use the following: 68008 (I have one and 8-bits simplifies my design) EPROM (2k or 8k) RAM (2k, 8k or 32K depending on how much code I wanted to run) 68681 (2 serial ports, timer, 6 bit input and 8 bit output port, built in baud rate generator, 68K async interface, runs off a 3.58 Mhz colorburst crystal) TTL oscillator ( I generally don't like trying to build crystal oscillators. Jameco is having a sale on 18.4320 parts at $1.95. Divide by 3 for system clock.) Glue TTL ('138 for decoding, maybe a delay if my ram/eprom isn't fast enough. DTACK generation (for EPROM and RAM), DTACK Detection (for 68681)) MAX-232 (RS-232 drivers. Only requires 5V. If I had a +-12V supply I'd use a MC145406 RS-232 driver chip) That's about $30-$50 in parts. The mounting hardware (breadboard, WW or soldertail sockets) will cost about 1/2 that. If I were doing anything more serious I'd use a 68010. The ability to change the interrupt vector, to move data between different address spaces and to have virtual memory support is worth the extra $20 bucks to me. I currently have a 10Mhz 68010 board with all the above components. It has 16K of EPROM and 128K of RAM running at no wait states. I use it as a Midi sequencer for my synth equipment. I'm in the process of putting together a 68008 board described above to test a WD2797 FDC chip I have obtained. The application notes can be quite helpful for designing system because they show various and sundry things like watchdog timers, interrupt handlers, interfacing to 6800 components. Another issue that hasn't been address is how are you going to program the beast. Without software any SBC is just another useless hunk of metal and silicon. My usual solution is to get a object code loader (usually Motorla S-records) running on the board's EPROM as quickly as possible and then develop software on another machine that has a cross assembler/compiler. I have one written in C for the 68681 Duart running at 9600 BPS. All it does is load and execute code. Fortunatly here at Tech I have access to Suns which I use to generate S-records from C code for my sequencer. Of course any number of public domain assemblers exist for the PC. A few can be found on the Motorla bulletin board (512-440-3733 8 bits no parity 300-1200-2400 bps). The best that I've found so far the a68k source on titan.rice.edu. It's a freely distributable C source version of the Dr. Dobbs assember that generates both S-records and Amiga object file format. If anything it does a little too much for you (like converting jumps to PC relative and zero filling S-records). One of the labs here has been using it to program the 68008 boards the students build for thier class project. Both of the above "features" has been removed. The rice version is in uuencoded zoo format. Both uudecode and zoo can be gotten from the comp.source.unix archives on uunet.uu.net. I wish you luck in your endeavor. If there's anything I can do to help just send mail to byron@pyr.gatech.edu. A question for Ed: Where can I get small quantity of 68HC11s and at what price? I'm thinking of doing a design for some control applications. Thanks a bunch. - -Ed Satterthwaite -ehs@src.DEC.COM or {...}!decwrl!ehs (ignore what our mailer says) BAJ -- Another random extraction from the mental bit stream of... Byron A. Jeff Georgia Tech, Atlanta GA 30332 Internet: byron@pyr.gatech.edu uucp: ...!gatech!pyr!byron