A 6809 Single Board Computer

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jmdlcar
Posts: 21
Joined: Tue Nov 12, 2019 8:08 pm

A 6809 Single Board Computer

Post by jmdlcar » Mon Jan 20, 2020 8:27 am

I'm going to build A 6809 Single Board Computer here is the link.

https://jefftranter.blogspot.com/2019/0 ... puter.html

If it works then I want to change the 68B09 to a 63C09 but I need to change the XTAL 7.3728 MHz to the one that will work with 63C09 so the CPU will run a 3 MHz.

Anyone have any idea?

sorchard
Posts: 419
Joined: Sat Jun 07, 2014 9:43 pm
Location: Norwich UK

Re: A 6809 Single Board Computer

Post by sorchard » Wed Jan 22, 2020 1:46 pm

Cool project. In fact I found quite a few interesting things to read about in your blog.

For operation at 3MHz, the uart may spoil the party somewhat and require a new board design. You would need a device that is rated for 3MHz and it would require a separate crystal to get a standard baud rate, namely a 12MHz xtal for the CPU and 1.8432MHz for the uart.

I imagine there could be a few uart options to look at. The WDC 65C51 is one possibility, but with a max baud of only 19200.

The 16550A supports higher baud rates, at the cost of extra glue logic for the bus signals.

Not forgetting of course that the access times of the memory devices need to be suitable for 3MHz operation.
Stew

jmdlcar
Posts: 21
Joined: Tue Nov 12, 2019 8:08 pm

Re: A 6809 Single Board Computer

Post by jmdlcar » Wed Jan 22, 2020 2:27 pm

If I leave it at the 68B09 @ 2MHz would there still be a problem?

sorchard
Posts: 419
Joined: Sat Jun 07, 2014 9:43 pm
Location: Norwich UK

Re: A 6809 Single Board Computer

Post by sorchard » Wed Jan 22, 2020 5:02 pm

If you have a 68B50 uart then it should run fine at 2MHz. You would just get a weird baud rate of 125k, which may or may not be usable with an FTDI cable, I'm not sure.

You may even be able to overclock it a little if you can find a suitable crystal (Maybe 8.9MHz?). I happen to have a terminal that has a 68B09 and multiple 6551 uarts running at 2.2MHz.

To get a standard 115200 baud you would need to connect the uart RXCLK & TXCLK inputs to a 1.8432MHz clock instead of E.
Stew

jmdlcar
Posts: 21
Joined: Tue Nov 12, 2019 8:08 pm

Re: A 6809 Single Board Computer

Post by jmdlcar » Wed Jan 22, 2020 6:19 pm

Here is the list of IC Chips

68B09
68B50
62256
74LS00
27C128

noggin32
Posts: 7
Joined: Thu Dec 14, 2017 8:36 pm

Re: A 6809 Single Board Computer

Post by noggin32 » Wed Jan 22, 2020 9:00 pm

I'm the person in the comments that says "I made one!" :D
It's based on a Grant Searle design: http://www.searle.wales/

I've tried many times to make this on a breadboard and failed.

Here's mine (with a homemade resistor array): https://c0dedbad.co.uk/6809.jpg
It worked first time. I would have made the tracks wider and the pads bigger.

Next is some peripherals.

I got a 74LS138 address decoder working. I can poke the 8 mapped addresses and see the enable spike on my scope.
That's as far as I got.

I forgot: I just received a AliExpress display that Ben Eater used in a video. Mine has a parasite SPI/I2C board that needs removing.

jmdlcar
Posts: 21
Joined: Tue Nov 12, 2019 8:08 pm

Re: A 6809 Single Board Computer

Post by jmdlcar » Wed Jan 22, 2020 9:36 pm

noggin32 wrote:
Wed Jan 22, 2020 9:00 pm
I'm the person in the comments that says "I made one!" :D
It's based on a Grant Searle design: http://www.searle.wales/

I've tried many times to make this on a breadboard and failed.

Here's mine (with a homemade resistor array): https://c0dedbad.co.uk/6809.jpg
It worked first time. I would have made the tracks wider and the pads bigger.

Next peripherals.

I got a 74LS138 address decoder working. I can poke the 8 mapped addresses and see the enable spike on my scope.
That's as far as I got.
I'm glad it work the first time for you. I just order all the parts I need to build 4 of them. When I order the PCB Board I'm thinking of ordering at least 5 or maybe 10. I do own a XGecu TL866II Plus High-Performance Universal USB Programmer so I can Burn the Eprom.
I wish I had the files "exbasrom and combined" I'm not how to compile them. Can you share them or all you have?

Why I'm going to built the first 3 I.) is for exbasrom 2.) is for combined and 3.) is for a 63C09 with exbasrom.

@71 and my birthday Feb 9 then I will be 72 I am retired with not much to do and later I will try to add other hardware to it. The EXPANSION HEADER I will try and see it I can use Rom Pak.

jmdlcar
Posts: 21
Joined: Tue Nov 12, 2019 8:08 pm

Re: A 6809 Single Board Computer

Post by jmdlcar » Wed Jan 22, 2020 9:59 pm

noggin32 wrote:
Wed Jan 22, 2020 9:00 pm
I forgot: I just received a AliExpress display that Ben Eater used in a video. Mine has a parasite SPI/I2C board that needs removing.
Not sure what mean?

noggin32
Posts: 7
Joined: Thu Dec 14, 2017 8:36 pm

Re: A 6809 Single Board Computer

Post by noggin32 » Thu Jan 23, 2020 7:49 pm

jmdlcar wrote:
Wed Jan 22, 2020 9:36 pm
I'm glad it work the first time for you. I just order all the parts I need to build 4 of them. When I order the PCB Board I'm thinking of ordering at least 5 or maybe 10. I do own a XGecu TL866II Plus High-Performance Universal USB Programmer so I can Burn the Eprom.
I wish I had the files "exbasrom and combined" I'm not how to compile them. Can you share them or all you have?

Why I'm going to built the first 3 I.) is for exbasrom 2.) is for combined and 3.) is for a 63C09 with exbasrom.

@71 and my birthday Feb 9 then I will be 72 I am retired with not much to do and later I will try to add other hardware to it. The EXPANSION HEADER I will try and see it I can use Rom Pak.
I think the minimum from JLCPCB (which I used) is 5 anyway. I didn't pay much.

Looks like the combined firmware is here:
https://github.com/jefftranter/6809/tre ... c/combined

There is a hex and a s19 file. Your EPROM programmer should support one of these.

The expansion header is where I have attached my 74LS138 address decoder.

jmdlcar
Posts: 21
Joined: Tue Nov 12, 2019 8:08 pm

Re: A 6809 Single Board Computer

Post by jmdlcar » Fri Jan 24, 2020 4:26 pm

@ noggin32

I order and the came today https://www.ebay.com/itm/Stackpole-Resi ... 2749.l2649 but way do the use as pin 1?

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