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Testa
Account closed
Registered: Oct 2004
Posts: 197 |
fetch the 0-sprite. with open borders...
hi,
ik have a little problem.. i want to open the sideborders with the 4 lowest sprites... i have two questions about it..
when i do the D016 write i use a dec d016 or a lsr or ror as opcode... why does a sty, sta, stx not work....
has it something to do with cpu takeover cycles at that point...
second question... what to do on a badline....
there are not enough free cycles. with 4 sprites for a inc, ror or lsr d016 instead of a sta, sty or stx...
i realize it is common knowledge.. but sorry i dont. know it...
bye...
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Oswald
Registered: Apr 2002
Posts: 5031 |
cool, glad we could sort it out afterall :) |
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chatGPZ
Registered: Dec 2001
Posts: 11148 |
the downside is: no i am curious about how they really did it. and there doesnt seem to be any 6502C datasheet online anywhere, and all the atari FAQs suck =P |
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Testa
Account closed
Registered: Oct 2004
Posts: 197 |
Quote: See this graph: In cycles marked with "X" (during takeover), writing is possible, reading not. RMW opcodes are special because their last *two* cycles are write-cycles. This way, you can still access the cycle yo need for opening the border. STA has just the final cycle as write cycle, that is not enough.
thanks ninja.. so on a good line there is no problem when you use RMW opcodes... but on a bad line it is not possible becoz BA will be low at cycle 56....
i have read the vic article about this and i understand it better now.....
well thanks anyway
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Monte Carlos
Registered: Jun 2004
Posts: 351 |
The discussion is very interesting, but perhaps a little too technical and therefore i doubt, that it is really helpful for someone asking about it.
There is one rule, which is probably more adequate:
- Use always the last sprites in row when opening the sideborder instead of the first ones and you will not experience most of these problems. So in this case sprites 4,5,6 and 7 would be appropriate.
Greetz Monte
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Mace
Registered: May 2002
Posts: 1799 |
Monte, that is the general rule.
Testa however wanted to find a way to use sprite 0, despite common knowledge that this is impossible.
Oh noes... did I say 'IMPOSSIBLE'...?
Now I triggered Crossbow! |
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Jetboy
Registered: Jul 2006
Posts: 229 |
Would it be possible to use sprite 0 with reu ? |
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Ninja
Registered: Jan 2002
Posts: 407 |
Technically yes. SuperCPU seems more fun to me, though. You can use the CPU while the VIC fetches data (as long as you don't access the c64-memory-map). |
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Monte Carlos
Registered: Jun 2004
Posts: 351 |
Why on earth would i use sprite 0, if i have 8 over n possibilities to assign all the sprites and get the same effect?
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Rastah Bar
Registered: Oct 2012
Posts: 336 |
Quote: See this graph: In cycles marked with "X" (during takeover), writing is possible, reading not. RMW opcodes are special because their last *two* cycles are write-cycles. This way, you can still access the cycle yo need for opening the border. STA has just the final cycle as write cycle, that is not enough.
Where can i find some info about this RMW stuff? In particular, is there some webpage where you can see for all instructions what is happening in each of the cycles? |
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MagerValp
Registered: Dec 2001
Posts: 1060 |
http://vice-emu.sourceforge.net/plain/64doc.txt |
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