San Bergmans NanoSBC 6802 - Page 1
Forum section: electronics / general

author: Phil_G
author_rank: Regular Contributor
timestamp: February 26, 2021, 12:33:14 am
content: Hi, I'm new here so I'm not sure if theres any interest in the MC6800/6802, I'm currently building a SWTPC 6800 clone/reproduction and along the way I built a couple of San's 6802 boards to get back into 6800 assembler (its been a while...). If there is any interest, I've written a monitor or bug for it, it does examine, modify, s-load, goto, calculates relative jump offsets, memory fill, breakpoints, and has vectored NMI & IRQ jumps, so its just like a 70's development system. It also has built-in a silly little noughts-&-crosses demo game!Here is Sans project:https://www.sbprojects.net/projects/nano6802/index.phpCheersPhil

author: woofy
author_rank: Frequent Contributor
timestamp: February 27, 2021, 11:19:20 am
content: Very nice, I just love these retro projects. The end result is usually about as useful as a chocolate teapot, but the fun along the way is priceless.The SWTPC 6800 sounds interesting too, any more information? Are you planning a reproduction case?

author: gslick
author_rank: Frequent Contributor
timestamp: February 28, 2021, 05:00:59 pm
content: I haven't really looked at the 6800 project there. I should take a look sometime.I do use the SB-Assembler there:https://www.sbprojects.net/sbasm/I originally used the DOS based Version 2. That is a pain now on current 64-bit systems where you have run it on an older OS in a VM.The current Version 3 is written in Python3 so it should be easy to run on any current system. Plus the source code is also available to download.It supports many of the popular vintage 8-bit CPUs if you're into that:https://www.sbprojects.net/sbasm/crosses.php

author: granzeier
author_rank: Regular Contributor
timestamp: May 03, 2021, 11:08:05 am
content: Quote from: Phil_G on February 26, 2021, 12:33:14 amYes, I also have some of San's boards and want to put some together. Could you post the source to your monitor, and the game, please?Thanks.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 03, 2021, 04:50:28 pm
content: Cool project. I would probably have favored the 6809 myself, as it was pretty advanced compared to the 6802, yet still in the same "family".But I reckon retro projects are not about "performance", so that's just a personal preference.

author: woofy
author_rank: Frequent Contributor
timestamp: May 03, 2021, 07:31:58 pm
content: I started with the Z80, but the 6800 was always a cpu I'd wanted to play with, but never had until very recently. I picked up up a Heathkit ET-3400 on ebay, and after some minor repairs its now fully working. I have to say, entering hex codes into a monitor program takes me way back. Not somthng you'd want to do too much of. I'm finding 6800 is a surprisingly capable processor considering its vintage..

author: Phil_G
author_rank: Regular Contributor
timestamp: May 17, 2021, 11:28:36 pm
content: Sorry for the late reply, I've uploaded the monitor, display board and a few other 6800/6802 bits & bobs here:philg.ukvia the Motorola link.Incidentally, has anyone been in contact with San? I've tried two email addresses but no response.CheersPhil

author: granzeier
author_rank: Regular Contributor
timestamp: May 18, 2021, 08:46:25 pm
content: Phil,Thank you for the code, looking it over now.I just received the final parts for my board, and will be putting one together soon. I wanted to use a ZIF socket for the EPROM, but it would not fit, so I am using a couple female pin headers to raise it up off the board enough to allow the capacitor to sit beneath the socket.

author: Phil_G
author_rank: Regular Contributor
timestamp: May 19, 2021, 12:37:01 pm
content: I added the keyboard overlay graphic to the link above but it will need scaling to suit the keypad - I drew it in Visio and it prints the perfect size, but saving it as a graphic changes the size for some reason(?)I printed it on ordinary paper then carefully covered it with wide sellotape on the front and double-sided tape on the back so it clings to the keys.Re the weird shape of the display board, its to clear the 4x4 keypad, its a bit tight as the two 6821 ports are very close and the display and keypad boards would otherwise overlap. That corner of the keypad needs clipping 45° too.The S19 loader expects to see TTL data on keypad Port B bit 7 at 300 baud. Theres no escape from a load, so when the load is done, and the display is showing 39 which is the S19 terminator, press Reset.Because the keypad and serial input share port B, press 'Load' first then connect the TTL serial line to B7 via an inline 1k resistor. Thats the loose yellow wire in the photo and video, I use a CH340G usb-to-serial adapter to power the board and Teraterm to optionally load S19 records.If you're still seeing yesterdays cached version of the 6800/6802 page, just tag a variable on the end of the url, that will force a reload, like sayhttp://www.mccrash-racing.co.uk/philg/6800/6800.htm?k=9CheersPhil

author: granzeier
author_rank: Regular Contributor
timestamp: May 31, 2021, 08:55:52 pm
content: Well, here is my try:In this first picture, none of the ICs have been mounted yet. Notice that the I/O section on the right-side of the picture has male header pins mounted from the bottom. This is so that I can mount the Nano onto a breadboard. I wanted to use a ZIF socket for the ROM so that I could swap the ROM chip easily, however the ZIF socket would not fit. So I used a couple male headers to lift the ZIF off the board, and it fits.Here the 6802 and the 6821 have been mounted. It looks like the ZIF socket is mounted on a slant, but it really is pretty level.I have a 2864 EEPROM to hold the program. Now all I need is to break out my programmer and get it running on my Linux system (it's for Windows - hopefully I can get it to run under wine.)First program will just copy one PIA port to another, connect a couple pushbuttons to the input port, and a couple LEDs to the output port. This will verify that the Nano works, and that I can control the PIA.

author: granzeier
author_rank: Regular Contributor
timestamp: May 31, 2021, 09:23:13 pm
content: By the way, I ordered 10 boards from Seeed Studios and have six left. If anyone would like one, I can pop it into a small letter envelope and send it first-class mail. Included will be my assembly notes and the Bill of Materials (BOM.) It will cost me $0.75 for anywhere in the Continental US, but more for out of the US. So, only people here in the US, please.If anyone else would like some boards to play with,https://www.seeedstudio.com/Motorola-MC6802-nano-Single-Board-Computer-(SBC)-g-1013152. There are a couple tiny differences between this board and San's, let me know and I can email you my assembly notes and the BOM (the board designer did not match up the component designations with the schematic

author: Phil_G
author_rank: Regular Contributor
timestamp: June 01, 2021, 09:25:52 am
content: Sorry I didnt realise that in the opening post I didnt give the link to the PCB on Seeed, yes thats the same board as in the video above (I also have a few spares!):Sans PCBWhen time permits I might remake the display and keypad on a proper PCB to match Sans 6802 board, that would neaten up the project, veroboard always looks 'temporary' to me!I do like the 6800/02, back in the day I found it to be one of the easiest for hand-coding - the monitors 'relative jump calculator' helps. As a background project I'm looking at a GAL as a single-chip decoder for rom, ram and io on Sans board, but I keep thinking the beauty of the original project is in its simplicity. Its not original of course, its the 'minimal system' documented by Motorola :-)Did you notice that San has the silkscreen annotation for the reset button is 90° out?CheersPhil

author: granzeier
author_rank: Regular Contributor
timestamp: June 01, 2021, 04:04:45 pm
content: Quote from: Phil_G on June 01, 2021, 09:25:52 amYeah, actually that Seeed board was not designed by San, it was designed by another guy. Unfortunately, he did not put any component values on his silk screen. I traced out all of the components, and came up with a BOM, which I can email (along with some other assembly notes) to anyone who would like.Also, I did not notice the reset button placement "error" myself (but it is mentioned on the Seeed Studio page.) I use a different 2-pin push-button (found them really cheap and bought several thousand.) All I needed to do was trace out the pins to the reset, and plug in my push-button - we shall see how well I did with that.

author: Phil_G
author_rank: Regular Contributor
timestamp: June 01, 2021, 08:14:47 pm
content: Thanks, I didnt know who did the boards so assumed it was San, the 'Barta' heading did make me wonderThe ancillary components are only pull-ups and decoupling, nothing is critical, I used 4k7 throughout and 100n.I used a cheap RS 4mhz crystal with 20pf either side. For ~A15 I found a BS170 in the junk drawer but I suspect any small fast N-channel EM would do. I do like EEPROMs instead of EPROM, so convenientIf you fancy doing the system above, TIL311s or DIS1417s are readily available on ebay for not much, and the keypad was only a couple of quid. Fun though, isnt it?CheersPhil

author: granzeier
author_rank: Regular Contributor
timestamp: June 01, 2021, 09:47:47 pm
content: Quote from: Phil_G on June 01, 2021, 08:14:47 pmYep, fun!I do plan on making something like yours, but the prices that I've seen for those displays are above what I'm willing to pay - especially for something that just takes binary and converts to hex. I've been doing that conversion for over 45 years, and have gotten pretty good at it.So, I'll just use discrete LEDs in my version. Also, I sell hex keypads in my store, so I'll just use one of those.

author: Phil_G
author_rank: Regular Contributor
timestamp: June 02, 2021, 09:43:54 am
content: Re the TIL311/DIS1417s, I've bought a few over the last couple of years, usually about £2 - £3 each which I thought was good value for a neat little display. IIRC ebay links are forbidden here but if you email or PM me I will pass on my links. Or you could try my eprom-plus-calculator-display idea from 'Back in the day' - I did a two-digit 'poor-mans TIL311' hex display using a 2716, half per digit, its described here:If you want to skip through, the relevant bit is 1:52 onwards... I still have the schematic and the hex dump, binary and assembler listing for the display eprom so its all repeatable if a bit clumsyCheersPhil