VERA Tile RAM Question

[Screech]

Ok. So I'm trying to understand how the VERA organizes the tile memory.

For a baseline, I'll use the Commodore 64 as an example.

If I wanted to manually "poke" a character into the Upper-Left corner of the screen, I'd POKE the Screen Code to 1024. Is there a corresponding POKE for the VERA (I'm using the term POKE loosely)? Also, how do i control the color of a specific tile (ie: C64 POKE 55296)?

I'm missing something obvious. I'm looking at the Programmer's reference guide and I'm sure the answer is there and I'm just not understanding it. My goal is to be able to VLOAD a screen directly into vera to display, and to use the screen color memory to mark areas the player has explored.

[Edmond D]

The C64 design is that the screen exists in the memory map which is available to the CPU, hence a POKE command to any CPU memory address works the same way, putting the value into the target memory address.

With the X16, the VERA video memory is outside the space of the main CPU's memory map. There are 32 registers used to interface the VERA to the X16 see https://github.com/X16Community/x16-doc ... ram-access for these registers in detail.

So an alternative approach has been created in BASIC - the VPOKE command. https://github.com/X16Community/x16-doc ... C.md#vpoke

What isn't explained in the help for VPOKE is the memory is set up with the first location being the character, the second memory location being the foreground and background colour of that character. The next character starts at $B002, it's colour and background is at $B003, and so on.

For the X16, you'd want to try something like:

VPOKE 1,$B000,1 : REM Put the character "A" in the upper left corner of the screen
(Note corrected a typo above that use to read VPOKE 1,$B000,1,1)

followed by

VPOKE 1,$B000+1,1 : REM make that "A" white on a blue background

Have fun playing around before you start going at VLOAD.

[Screech]

Thanks. That solves a lot of issues for me.

[DusanStrakl]

You might want to check some of tutorials on my blog:

https://www.8bitcoding.com/p/blog-page.html

I recommend you check the VERA Overview first and then depending if you want to work in BASIC or Assembly check few more in depth articles to understand concepts of TileBase and MapBase and how they are organized and manipulated.

[schristis]

VPOKE 1,$B000,1,1 : REM Put the character "A" in the upper left corner of the screen

followed by

VPOKE 1,$B000+1,1 : REM make that "A" white on a blue background

Have fun playing around before you start going at VLOAD.

I Just found this out !!! I knew you could do it on the C64.... but the VERA has been more complicated ~
There are no examples I would have found to tell me this !

Here is a screenshot of how this works (I had to experiment) because there aren't examples !


That Awsome....
Just 1 thing.... VPOKE 1,$B000,1,1 is a mistake gives a syntax error also~ it should be
VPOKE 1,$B000,1 (no ,1 at the end) I have fat fingers too

also DusanStrakl, I've been using your examples to create sprites. They've been very helpful. Thankyou.

You might want to check some of tutorials on my blog:
https://www.8bitcoding.com/p/blog-page.html

Thankyou for this
Best Regards
Shaun

VPOKE.JPG (135.03 KiB) Viewed 7084 times

[Edmond D]

Glad that you've got it to work!

There are no examples I would have found to tell me this !

Agreed - the VPOKE example in https://github.com/X16Community/x16-doc ... 20BASIC.md could be better. To be fair, it is a reference guide and not a tutorial book.

Just 1 thing.... VPOKE 1,$B000,1,1 is a mistake gives a syntax error also~ it should be
VPOKE 1,$B000,1 (no ,1 at the end) I have fat fingers too

The typo was more of a case of my OS not being fully booted up, rather than fat fingers. I usually create posts/replies in the morning which leads to theses types of mistakes.

Thanks for pointing it out! I've gone back and edited the original post so the next person doesn't get caught, nor do they have to read the whole thread.