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RE: [N8VEM-S100:3389] S-100 boards in work - uPD7220

Guys before we go to C code etc., is the a simple chip initialization routine such that at least one line or character can be placed on the screen to check out the hardware.   Preferably in Z80 or 8086 code.





From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of yoda
Sent: Wednesday, April 30, 2014 7:00 AM
To: n8vem...@googlegroups.com
Cc: mon...@vitasoft.org
Subject: Re: [N8VEM-S100:3389] S-100 boards in work - uPD7220




I think if you are going to be an earlier tester of this board you need to be able to do hardware support as well.  This board "should work" as it is based on the N8VEM ECB design.  There will probably be some complications.  Porting the software is the least of the work - transcribing from one language to another is not that hard with software that already works.  It is also much easier if the software is written in a somewhat higher language than assembler.  My plan is I will write my code in C that will run on the 68K using gcc cross compiler, Z80 with SDCC and could run on x86 with gcc cross compiler though I don't plan to test that as I don't have any plans for using or supporting x86 as I just don't like the architecture of x86 in general.  I believe there is a C compiler for 6502 as well but have not delved into that yet.  It is fun to write assembler once but it is not productive to do it much more.  The monitor I have written for the 68K is > 99% C is a derivative of John's monitor but I am doing in a way that should be portable.  My next target will be to port this to z80.  The monitor is straight forward for z80 I think - the interface to CPM may be a little more challenging.  I am not done yet still getting s-record load and IDE disk running.  Also I need to do some more refactoring - not happy with it yet.  I will post the portable version when it is further along, i.e., boots CPM 68K.


So the net of this is - this board is more of a hardware bring up not a software driver project, so if you are not comfortable with hardware bring up you probably should not be one of the early users of the board and wait till the board is debugged and a second round of boards are produced with any changes.



On Wednesday, April 30, 2014 5:45:49 AM UTC-5, David Fry wrote:

Hi John,


I'm re-posting in case you missed my earlier post.


We have 3 volunteers to work on software for 3 different processors for the Prototype S100 uPD7220 GDC Board,

I'd just like to clarify if your offer to provide hardware support is still open, if so how many PCB's would you need ?

I anticipate this being a longer term project so hopefully shouldn't call on you too often :-)


Todd has offered to co-ordinate the PCB procurement and distribution.

I have uploaded the modified KiCad files to the Wiki, the only changes were to replace the 15 pin Dsub connector for a 2 x 8 IDC connector wired the same as the console i/o board, and updated the board identifier text (bottom right corner) Andrew has checked the schematic change and has given it the OK

So if everyone is happy then I guess we are ready to order.



regards and thanks


David Fry

On Saturday, April 26, 2014 5:56:07 PM UTC+1, monahanz wrote:

I think we need to do a prototype run on that board first.  While it contains elements of 3 previous boards we did,  it is the first time they are all put together in one place.  Also as a few of us know, we had real problems with that BT478 chip on the VDP board (which itself BTW needs to have another prototype run).


On the 7220 I will help out with the hardware, the thing to remember about the 7220 is you have to do quite a bit of software writing to get it to be of any use.   Is somebody prepared to do that. Because without software that chip/board  is useless.





From: n8ve...@googlegroups.com [mailto:n8ve...@googlegroups.com] On Behalf Of David Fry
Sent: Saturday, April 26, 2014 7:40 AM
To: n8ve...@googlegroups.com
Subject: Re: [N8VEM-S100:3295] S-100 boards in work


Hi Ed,


Andrew has uploaded the EDA files for the uPD7220 GDC this afternoon, if you feel inclined to do a production run then put me down for 1 board

just for curiosity value. It might be worth considering a smaller run of 5 to 10 boards as this board has failed to spark sufficient interest for a production run

before. looking a previous forum posts for the uPD7220 GDC it would appear to be a descendant of the ECB uPD7220 graphics board interfaced to the S100 bus and is ripe for testing.





David Fry

On Friday, April 25, 2014 11:19:04 PM UTC+1, Edward Snider wrote:

It does seem like it would be an interesting board for an S100 system.  

With almost all of the work done it would be a shame not to go through to completion.


Unfortunately I don't have enough of a system together to help in testing, but I can chip in a bit

for prototypes.  I'd also be willing to handle the production run if we can get takers for at least

20 boards, if that would be helpful.




On Tuesday, September 24, 2013 1:45:38 AM UTC-5, nekonoko wrote:

Hi Andrew,

I can definitely see chipping in at least some of the cost. I find the uPD7220 GDC interesting as several business class CP/M systems used it for graphics (DEC Rainbow, QX-10 etc.).

Thanks much,


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