Sinclair ZX80 / ZX81 / Z88 Forums

A new plug in board that allows the use of external WRX enabled memory such as that found on ZXpand, ZXpand+ and ZXblast to be used for User Defined Graphics is now on sale over at sell my retro

https://www.sellmyretro.com/offer/detai ... pand-28480

Regards Andy

Well, at least you now have sold one

Mark

I ordered the second and like to test it out with ZXblast.

I think this board will allow H4TH together with a standard Zeddy together with ZXblast to get the different charset somehow in the chip. Can it be downloaded ? Didn't read instructions carefully but guess this will work somehow. Would be nice to be downloaded directly from ZXblast. We will see what is possible. But sounds interesting.

Maybe need some help from Erik to get H4TH properly run on ZXblast. Of course an improved firmware would be necessary, I think.

PokeMon wrote: ↑Thu Aug 24, 2017 9:37 pm I ordered the second and like to test it out with ZXblast.

I think this board will allow H4TH together with a standard Zeddy together with ZXblast to get the different charset somehow in the chip. Can it be downloaded ? Didn't read instructions carefully but guess this will work somehow. Would be nice to be downloaded directly from ZXblast. We will see what is possible. But sounds interesting.

Maybe need some help from Erik to get H4TH properly run on ZXblast. Of course an improved firmware would be necessary, I think.

Hi Karl, Mrtinb has been testing the board with ZXblast and has reported sucess, however his findings also revealed a possible conflict with ZXblast and Zon-x as some of the programs he tested were zon-x enabled and would crash after some minutes, when other programs that were not zon-x would not crash.

the UDG board emulates some of the ULA to provide the alternate address buss to the memory device ( zxpand or zxblast or other wrx enabled ram) during refresh only, the address of the character set is controlled in the normal way by altering the I Register.

regards andy

One of the question is how the UDG can be stored on the board. I didn't try out your UDG editor yet but I can extract the complete charset from the ROM file and would be nice if there is any download option. Putting this into a p file would be an option (or overwrite the buffer) - direct access would be nice. Is the UDG stored permanently on the disk/flash or whatever you use ?

About ZON-X, there shouldn't be a conflict with standard IO addresses (xFh) but there is a conflict with the second ZON-X (6 channel sound) and with ZXpand. This is because the A3 bit used (low) for addressing ZXblast internals. There is a new series of ZXblast on the way with full address decoding to avoid those conflicts. I think I could provide a small adapter board to be put on the address jumper socket to get full address decoding for the first series of ZXblast.

I think I can test some games later with my Mr.X card (need new GAL as I think it is broken or lost program - GALs are not very reliable ...).

PokeMon wrote: ↑Thu Aug 24, 2017 10:46 pm One of the question is how the UDG can be stored on the board. I didn't try out your UDG editor yet but I can extract the complete charset from the ROM file and would be nice if there is any download option. Putting this into a p file would be an option (or overwrite the buffer) - direct access would be nice. Is the UDG stored permanently on the disk/flash or whatever you use ?

UDG's are not stored on the board, one must first load, copy from rom, create from scratch ect... for starts you could simply use the DKCHR.ROM loaded at 8192, or to use your own characters you would first design them using the UDG designer, save them to storage and then you can reload that character set when ever a specific program requires it. Changing the i register takes only 5 bytes so can be poked into a line 1 rem statement so charsets can be used easily from basic also.

regards andy

QUOTE.

"Changing the i register takes only 5 bytes so can be poked into a line 1 rem statement so charsets can be used easily from basic also."

This is the bit that leaves me stumped.
I have created some UDG's but don't know how to display them using basic any chance of a simple example, say a line of "X"'s being turned into a UDG of my choice?

I assumed no I-register needed to be changed. I assumed your chars should just be at memory location 8192 - 8704. Or 8192 - 9216 with CHR$128.

Andy Rea wrote: ↑Thu Aug 24, 2017 11:06 pm UDG's are not stored on the board, one must first load, copy from rom, create from scratch ect... for starts you could simply use the DKCHR.ROM loaded at 8192, or to use your own characters you would first design them using the UDG designer, save them to storage and then you can reload that character set when ever a specific program requires it. Changing the i register takes only 5 bytes so can be poked into a line 1 rem statement so charsets can be used easily from basic also.

regards andy

If I understand you right then the board uses only the memory (of ZXblast for example) to display the UDG stored there ? That would be simple to realize (fill that area with proper data at instance startup). Can be I register pointing anywhere to RAM or ROM ? What if I register pointing to the first 8k with a different ROM 0-8k ?

So now a changed ROM can be put on ZXblast for any instance in ZXblast ROM but during the short refresh period the ZXblast internal ROM is disabled and let the original ZX81 ROM enable. So I guess it would take the internal charset as UDG. Probably UDG is required to be in a region 8k-64k, right ?

Moggy wrote: ↑Fri Aug 25, 2017 11:35 am QUOTE.

"Changing the i register takes only 5 bytes so can be poked into a line 1 rem statement so charsets can be used easily from basic also."

This is the bit that leaves me stumped.
I have created some UDG's but don't know how to display them using basic any chance of a simple example, say a line of "X"'s being turned into a UDG of my choice?

The 5 bytes in M/C are necessary to change the I register to point to another UDG-character set in RAM. You could use standard POKE command to store the UDG pattern there by BASIC.
I have done that also in my UDG game:
viewtopic.php?f=6&t=526&p=4987&hilit=Interc+u#p4987

Regards
Siggi