RetroBrew Computers Forum
Discussion forum for the RetroBrew Computers community.

Home » RBC Forums » General Discussion » New board: V20-MBC, an easy to build V20 SBC (and a prototype on breadboard) (V20HL CPU (uPD70108H) or 80C88 CPU @ 4/8MHz, CP/M-80 and CP/M-86, 128/512/1024KB RAM, I2C, Serial, ISP, User led and key, optional RTC and microSD, optional 16x GPIO port)
Re: Starting V20 CPU on breadboard. [message #7560 is a reply to message #7559] Tue, 21 April 2020 08:55 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 178
Registered: May 2017
Location: Dark side of the Moon
Senior Member
I've just uploaded on the V20-MBC page (https://hackaday.io/project/170924#menu-files) all the details to build it, including the Assembly guide, BOM, etc.

Also I've released the IOS and the content of the related SD.

There isn't any OS for now, but you can use a couple of Basic interpreters and the Fig-Forth v1.3 (8080 mode).

The option 4 loads the IMSAI Basic as default configuration.

The option 3 loads a HelloWord demo as default configuration.



@gkaufman:
yes, you can use HCT. I've used some too.

@mikemac:
as gkaufman already said...

Re: Starting V20 CPU on breadboard. [message #7561 is a reply to message #7560] Wed, 22 April 2020 01:14 Go to previous messageGo to next message
Yves-D. is currently offline  Yves-D.
Messages: 14
Registered: January 2020
Junior Member
@just4fun
What would be the prerequisites of running MS-DOS and DOS-text-based appliations on the V20-MBC?
There you could tap into a large software repository.
I guess, DOS relies heavily on (non-existent) BIOS-Calls for user and I/O interaction.
A complex editor like the one in TurboPascal 7.0 perhaps also relies on a (non-existent) graphics-card, if it would bypass the BIOS-Calls for speed and switching to 80x43 character mode for example.
Re: Starting V20 CPU on breadboard. [message #7562 is a reply to message #7561] Thu, 23 April 2020 00:28 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 178
Registered: May 2017
Location: Dark side of the Moon
Senior Member
@Yves-D.

Using a custom BIOS probably it should be possible to run MSDOS with restrictions due to the lack of a video card, so only "text programs" could run here (using only BIOS calls).
This means that the custom BIOS should "remap" the text video I/O on the serial port (using VT100-like cursor control).
I haven't analyzed that in detail yet...

Re: Starting V20 CPU on breadboard. [message #7591 is a reply to message #7562] Sat, 02 May 2020 04:26 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 178
Registered: May 2017
Location: Dark side of the Moon
Senior Member
The current IOS (S263020) has a bug preventing a running program to read date/time as expected.

To fix overwrite line 2060 of S263020.ino:

  if ((ioOpcode != 0x0A) && (ioOpcode != 0x0C)) ioOpcode = 0xFF;    // All done for the single byte opcodes.

with the following:

  if ((ioOpcode != 0x84) && (ioOpcode != 0x86)) ioOpcode = 0xFF;    // All done for the single byte opcodes.

It will be fixed in the next revision.

[Updated on: Sat, 02 May 2020 04:31]

Report message to a moderator

Re: Starting V20 CPU on breadboard. [message #7658 is a reply to message #7591] Sun, 17 May 2020 16:29 Go to previous messageGo to next message
gkaufman is currently offline  gkaufman
Messages: 163
Registered: October 2015
Senior Member
I've been having trouble locating D70108HCZ processors that weren't Chinese remarked parts.

Decided to try some V20's I had lying around including D70108D-8 and D70107C-8.

Surprisingly both booted right up at 8mhz and seem to be working fine, at least with some minimal testing.
Re: Starting V20 CPU on breadboard. [message #7660 is a reply to message #7658] Mon, 18 May 2020 01:36 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 178
Registered: May 2017
Location: Dark side of the Moon
Senior Member
gkaufman wrote on Mon, 18 May 2020 01:29
Decided to try some V20's I had lying around including D70108D-8 and D70107C-8.
Surprisingly both booted right up at 8mhz and seem to be working fine, at least with some minimal testing.

Interesting. I've some D70108C too...

BTW: starting to play with CP/M 2.2 using the 8080 mode:

/forum/index.php?t=getfile&id=1793&private=0
Re: Starting V20 CPU on breadboard. [message #7677 is a reply to message #7660] Wed, 20 May 2020 10:22 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 178
Registered: May 2017
Location: Dark side of the Moon
Senior Member
The new IOS with CP/M 2.2 (8080 mode) support is out here:

/forum/index.php?t=getfile&id=1797&private=0
Re: Starting V20 CPU on breadboard. [message #7688 is a reply to message #7677] Sat, 23 May 2020 08:53 Go to previous messageGo to next message
gkaufman is currently offline  gkaufman
Messages: 163
Registered: October 2015
Senior Member
CP/M came up nicely, thanks again for your efforts!
Re: Starting V20 CPU on breadboard. [message #7753 is a reply to message #7688] Thu, 04 June 2020 11:10 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 178
Registered: May 2017
Location: Dark side of the Moon
Senior Member
CP/M-86 is out!

Update here both IOS and the SD image.

/forum/index.php?t=getfile&id=1801&private=0

/forum/index.php?t=getfile&id=1802&private=0

[Updated on: Thu, 04 June 2020 11:10]

Report message to a moderator

Re: Starting V20 CPU on breadboard. [message #7754 is a reply to message #7753] Thu, 04 June 2020 12:32 Go to previous messageGo to next message
Yves-D. is currently offline  Yves-D.
Messages: 14
Registered: January 2020
Junior Member
Yay, great. Thanks for all the work you did there. Lovely!
Re: Starting V20 CPU on breadboard. [message #7757 is a reply to message #7754] Fri, 05 June 2020 08:31 Go to previous messageGo to next message
gkaufman is currently offline  gkaufman
Messages: 163
Registered: October 2015
Senior Member
CP/M-86 came up easily.

Reminds me of the old CompuPro 8085/8088 S-100 board.

Thanks!

[Updated on: Mon, 08 June 2020 05:23]

Report message to a moderator

Re: Starting V20 CPU on breadboard. [message #7773 is a reply to message #7757] Wed, 10 June 2020 08:46 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 178
Registered: May 2017
Location: Dark side of the Moon
Senior Member
I've just released a new SD image that adds in the drive F: of the CP/M-86 Disk Set a CP/M-80 emulator under CP/M-86 using the V20 8080 mode (VCPM15.CMD).

In this way it is also possible run Catchum or send/receive a file with XMODEM:

/forum/index.php?t=getfile&id=1803&private=0

As a curiosity I've also added a pure SW emulator (8080.CMD)

For more info read the README.TXT file in the F: drive.

[Updated on: Wed, 10 June 2020 08:47]

Report message to a moderator

Re: Starting V20 CPU on breadboard. [message #7893 is a reply to message #7773] Mon, 03 August 2020 07:29 Go to previous messageGo to next message
bigpete is currently offline  bigpete
Messages: 2
Registered: May 2020
Junior Member
I ordered my PCBs for this today. This is going to be my first build and am looking forward to getting it up and running. Now just to source the V20...

Re: Starting V20 CPU on breadboard. [message #7924 is a reply to message #7893] Sat, 22 August 2020 22:08 Go to previous messageGo to next message
dittman is currently offline  dittman
Messages: 3
Registered: February 2019
Junior Member
Does anyone have a pre-built BOM for Mouser or Digi-Key for this board?
Re: Starting V20 CPU on breadboard. [message #7925 is a reply to message #7924] Mon, 24 August 2020 02:56 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 178
Registered: May 2017
Location: Dark side of the Moon
Senior Member
Just destroyed the "V20 on breadboard"...

/forum/index.php?t=getfile&id=1831&private=0

to start a new toy...

/forum/index.php?t=getfile&id=1832&private=0

but this one will be another story...
Re: Starting V20 CPU on breadboard. [message #7926 is a reply to message #7925] Thu, 27 August 2020 11:25 Go to previous messageGo to next message
guus.assmann is currently offline  guus.assmann
Messages: 32
Registered: May 2018
Location: Netherlands
Member
Hello,

What files should I program into the Mega32A?
I have a Hi-Lo ALL programmer that can program the Mega.
How should I set the fuses, what file goes into the Eeprom and what goes in the flash?

Thanks for a very nice design.
I'm working on getting ist to the same bus as the SBC-85.

BR/
Guus Assmann
Re: Starting V20 CPU on breadboard. [message #7927 is a reply to message #7926] Fri, 28 August 2020 00:24 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 178
Registered: May 2017
Location: Dark side of the Moon
Senior Member
@guus.assmann:

Hi, all the related files are here: https://hackaday.io/project/170924/files

You have to flash the .hex file into the Atmega32. Nothing more. The fuse bits are written in the description of the .hex file (High Byte 0xD6, Low Byte 0xAF, Lock Byte 0xCF).

Regards.

[Updated on: Mon, 31 August 2020 11:31]

Report message to a moderator

Starting V20 CPU on breadboard. [message #7960 is a reply to message #7927] Thu, 10 September 2020 00:52 Go to previous messageGo to next message
guus.assmann is currently offline  guus.assmann
Messages: 32
Registered: May 2018
Location: Netherlands
Member
Hello,

For the "sister project" with the Z80, it's possible to go to 20Mhz.
Can this be done for the V20 as well?

And I've been bussy for a bit.
You may know of the SBC-85 project, that has a backpanel.
Both the Z80 and V20 have been routed by me, to fit this bus.
The PCB's have not been tested yet. And some checking of the schematics would be nice.
I'll try to publish these schematics this evening.

BR/
Guus
Re: Starting V20 CPU on breadboard. [message #7961 is a reply to message #7960] Thu, 10 September 2020 03:04 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 178
Registered: May 2017
Location: Dark side of the Moon
Senior Member
Hi, the clock is provided by the Atmega32, so 8MHz is the max.

Please note that the Z80-MBC and V20-MBC design is not intended for the use on a external bus. This could require a deep re-design. How deep depends on the reference bus logic and electrical requirements.
Starting V20 CPU on breadboard. [message #7963 is a reply to message #7961] Thu, 10 September 2020 06:21 Go to previous messageGo to next message
guus.assmann is currently offline  guus.assmann
Messages: 32
Registered: May 2018
Location: Netherlands
Member
Hello,

Thanks for the comment.

Maybe I should be a bit more clear. Embarrassed
For the Z80, it may be possible to overclock the Mega32. As this is out of spec, some luck is needed.
And I wonder if the same can be done for the uPD70108 board.
To me, both designs look very similar in the Mega32A part. (And the uPD70108 I have is rated for 16Mhz and the memory is faster than 55nS)

As for the PCB's I've routed, basically what I've done is get very many signals to the bus.
I assumed that it should be possible to connect some I/O on the bus.
For that, I'm thinking of a 82C55 and other "simple" I/O.
Maybe some memory is possible as well. Of course the addresses should not "clash".
The bus monitor may also work for the major part. (I often like blinking lights and numbers. Laughing Wink

BR/
Guus

[Updated on: Thu, 10 September 2020 06:21]

Report message to a moderator

Re: Starting V20 CPU on breadboard. [message #7964 is a reply to message #7963] Thu, 10 September 2020 09:05 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 178
Registered: May 2017
Location: Dark side of the Moon
Senior Member
Ah... yes, you can overclock the Atmega32 @ 20MHz and this should work without any particular problem.

I've done it with the Z80-MBC2 (read here) and could also be done with the V20-MBC (but I haven't tested in this case).

About the external bus, you need to make changes in the design to allow external I/O to access the bus without data clash.
It is not possible just to bring the signals to an external connector... (for both the boards)

E.g.: on the Z80-MBC2 the Atmega32 just "senses" the A0 line simply ignoring all the others address lines. So in your case you must change this logic.
You have to re-check and analyse the whole I/O addressing logic of both the boards to find what to change in your case. Also the logic that puts the CPU in wait must be changed.

About using external memory, all the memory addressing space is already fitted.

Good luck!

[Updated on: Thu, 10 September 2020 09:10]

Report message to a moderator

Starting V20 CPU on breadboard. [message #7965 is a reply to message #7964] Thu, 10 September 2020 10:41 Go to previous messageGo to next message
guus.assmann is currently offline  guus.assmann
Messages: 32
Registered: May 2018
Location: Netherlands
Member
Thanks for the info.
And just in case, I'll upload the schematics.
So this setup cannot do too much, other than having a peek on the busses.
The monitor card of the SB-85 may (partially) work, as a display device anyway.
I'm not sure if I'll be able to change the logic / program to do some more usefull things.
It will be quite a challenge.....

BR/
Guus
Re: Starting V20 CPU on breadboard. [message #7971 is a reply to message #7965] Tue, 15 September 2020 15:51 Go to previous message
ab0tj is currently offline  ab0tj
Messages: 70
Registered: October 2015
Location: Colorado
Member
Has anyone gotten MSDOS booted on one of these yet?
Previous Topic: Cyclone II and IV boards available.
Next Topic: Registering for wiki and resetting passwords not working?


Current Time: Sun Sep 27 14:35:40 PDT 2020

Total time taken to generate the page: 0.01575 seconds