Posted By
Uto
on 2019-12-23
10:50:40
|  Re: Read from RAM and colour area
Thank you for your response SVS. In fact I just don't write to $FF06 amymore, that's why I found this issue. What I do is:
1) Page in ROM (write to $FF3E)
2) User KERNAL functions to read file
3) Write text read from file on screen
4) Page in RAM
What happens is just after point #1 all the attributes on screen change to random values, so I get multiple colour 8x8 squares. The bitmap data though remains the same, you can still see the picture pixels and the text letters below those messed colors. Them, when point #4 happens, all attributes come back to previous status.
That's why I think that the bitmap data is being read from RAM, but the luminance and colours data is being read from ROM.
Regarding your point #2 it's a interesting information, but I've checked and I don't see any code writing to RAM that can affect the attributes area randomly, and as the attributes are restored to the proper ones when I page in RAM again, it means RAM has not been modified.
Your third point is very interesting to know, it could led to misunderstandings, but I have checked the game without even opening the monitor and same thing happens.
Thanks again for your response, the more I know, the easier is I found a solution.
PS: These are three pictures that show how the screen is before paging in ROM, while ROM is paged, and how it looks after RAM is paged in again.
Before:
htt://drive.google.com/file/d/1cyo5OVewvv31krn7AYvH6rmmqMOWf4g9/view?usp=sharing
Meanwhile:
htt://drive.google.com/file/d/1NtP_xyjmAe-qEQ9bHyZm_QJnlkq8qvU-/view?usp=sharing
After:
htt://drive.google.com/file/d/1ueaLOtiRvpyW024o0gAeB7GXdYj_xeSk/view?usp=sharing
Please add the missing "p" to the http links above, I had to remove them cause otherwise the forum thinks it's SPAM. Sorry for that.
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