I modified my software to insert the above values in all the above registers.
Unfortunately it did not work, however the screen does look different and seem like it is continuously writing spaces sequentially to the whole screen in some kind of high resolution mode.
Because with this set of registers' values pattern generator table is located starting 1000h. Replace "LD A,48H" with "LD A,50H" in line 237.
flyguille, thanks for the above information. Appreciate the time and effort.
I modified my software to insert the above values in all the above registers.
Unfortunately it did not work, however the screen does look different and seem like it is continuously writing spaces sequentially to the whole screen in some kind of high resolution mode.
I’m wondering if I have the character generator or something else placed wrong.
I have made a link specifically for you at the bottom of this page
http://s100computers.com/My%20System%20Pages/VDP%20Video%20B...
Under "For Leon" there is a "here" link that contains a .zip file with the above source code.
Do you know where specifically the start address of your screen character generator.
Is source for it available.
John
ok, seems like a double,
please count the exact ammount of lines and rows before that it repeats all the text, that number must be a hint for what is wrong in the vdp or memory bank.
I modified my software to insert the above values in all the above registers.
Unfortunately it did not work, however the screen does look different and seem like it is continuously writing spaces sequentially to the whole screen in some kind of high resolution mode.
Because with this set of registers' values pattern generator table is located starting 1000h. Replace "LD A,48H" with "LD A,50H" in line 237.
try to print more character, from 0 to 255, to see if the patterns are wrong somehow.
if the pattern table is not affected, can't be a problem with vram addressing , but maybe that specific v9938 is faulty.
post here the code that are you using to setup vdp & print that string.... all the whole thing.
flyguille, that did the trick!!!
Changing to LD A,50H gave me a clean 80X24 display. I have a (poor) picture of it here:-
http://www.s100computers.com/My%20System%20Pages/VDP%20Video...
bottom of the page.
THANKS SO MUCH FOR YOUR HELP. I, and I'm sure other S100 users will appreciate the time and effort.
I still have much to do here. For example right now I can only get an 80X24 display if I first configure the chip to display 40X24. Two separate programs. I'm not worried, clearly another initialization bug. The main comfort I have is it now looks like the hardware is sound.
On the hardware, it does not seem to matter how the A6 & A7 address lines are connected to the DRAM. However based on your point that the MSX boards have them flipped I will do it on this board also. Must be something to do with refresh.
One software point, I’m using the original IBM-PC CGA video board character table. Seems to work fine except that characters with decenders like “y” “q” etc. have their bottoms cut off. Is there a trick to changing the scan line, or does the MSX character set fudge it by using a smaller character?
Is there a source/listing for the MSX table?
MSX uses 6x8 characters.
Indeed a 16-bit the MSX II (1985) and MSX II-Turbo (1988) standard was announced. However by 1990 even Sony Corporation (MSX's strongest supporter) , gave up on supporting MSX.
Can you please fix this nonsense? See the "What is MSX?" part of the Wiki of this web site.
flyguille, that did the trick!!! Changing to LD A,50H gave me a clean 80X24 display.
Hm... after the issue is solved I wanted to write short summary on the case, not sure if it makes sense now 
My posts kinda not getting much attention and credibility here...
openMSX guys: How to I redirect the output of the command "vdpregs" to a file? (or any console commands, BTW)
I usually redirect it to stderr and copy/paste it from the terminal I started it on.
puts stderr [command]
It works fine for vdpregs, but unfortunately it doesn't seem to work for toggle_vdp_access_test.
Yes, because the output of the command itself is different than the output that the script generates. You could modify the script (just add stderr behind the puts commands in the script). (There are other ways, but those are a bit harder to explain here.)
After some googling, I've found a nifty way described in this forum thread and I would like to share it here:
On openMSX console, type:
close stdout open /tmp/openMSX.out toggle_vdp_access_test close stdout
It works like a charm! The output of toggle_vdp_access_test (or any other script, for that matter) ends up in the /tmp/openMSX.out file. :)
