Posted By
MMS
on 2023-04-09
06:45:41
 |  Re: YAPE 1.2.2!
Well, I own a SID card. It is great that mouse on SID Card is supported via YAPE. But how you can really use it?
Fortunately I still have the SID documentation.
I read some forums on the 1351 mouse and I think I see some contradictory information how to use the 1351 mouse coordinates.
SID chip documentation says, that the X and Y position stored in 8 bit
https://www.c64-wiki.com/wiki/SID
1351 information say the positions are store only on 6 bits (1-6) in modulo 64 coding.
It means, that X position 65, 129, 193, 257 gives the same result on the register, 1.
In case of the later version, how you know the exact position from the 320 HIRES positions? or it was never intended to use such high precision?
https://www.c64-wiki.com/wiki/Mouse_1351
And a more detailed explanation
https://www.commodore.ca/manuals/funet/cbm/manuals/1351-mouse.txt
So the SID register shows the CHANGE compared to the previous 512 microseconds position, or really STORES the X coordinte of the mouse?
The how you know which position from the aboves it shows?
(just to mention, it is a strange approach from Commodore. I know originally the used for paddle only, but there are some SID registres when the half byte "not used", like Filter cut-off freuency low byte, and such... they could store the full 320 coordinate (X positions) on 9 bits, 512 values, but they choose Modulo 64 coding)
On C64 / SID the Y coordintae reversed (also a strange behavious on C64 that it behaves the opposite way as the hires and charmap coordinate system),not like on Amiga AtariST mouse.
One more conclusion: ATARI ST mouse and Amiga mouse could be used on NST SID card. I think it is NOT a widely known information!
(though the prices are rather similar to 1351 on ebay)
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