must WSYNC be called before HMOVE?

[antron]

can one just wait until 6502 cycle 0 and write to HMOVE, or must WSYNC be written to first? i want to save 3 cycles in my kernal, but move things too.

thanks,

antron

[Bruce Tomlin]

If you know you'll be on cycle 0, there should be no difference.

 

Also, I'm pretty sure I've seen that HMOVE works fine in the first few cycles of a scan line. More than ten cycles or so, and you start getting into the wierd stuff that has you seeing stars.

[antron]

the emulator i am using (stella 1.4.2_cvs, linux) flips out. i'll see if i can get it stabe on my vcs.

thanks

 

wait, i think i have it now. this will rock if i can get those 3 cycles

Edited June 15, 2005 by antron

[+batari]

If you know you'll be on cycle 0, there should be no difference.

 

Also, I'm pretty sure I've seen that HMOVE works fine in the first few cycles of a scan line.  More than ten cycles or so, and you start getting into the wierd stuff that has you seeing stars.

874421[/snapback]

I've found it also works when you call it a cycle or two early, like on cycle 74 or 75. Not sure why it works, maybe because the actual store will take place after cycle 76/0?

[Bryan]

HMOVE can be called at any time, but it only has an effect on position during the H-blank period, and it only works as described when called right after a WSYNC. Read this for more info on how HSYNC works:

 

http://www.atarihq.com/danb/files/TIA_HW_Notes.txt

 

-Bry

[antron]

OK it is stable now, with no WSYNC. But now I realize how nice they were before. Now I have to be aware of all page boundries. One of my two loops needs one extra cycle, and they are identical in cycle counts. WSYNC was cleaning it up for me. Oh well, I guess thats what absolute reads/writes to page one are for.

[Thomas Jentzsch]

Oh well, I guess thats what absolute reads/writes to page one are for.

Or careful data alignment.

[vdub_bobby]

HMOVE can be called at any time, but it only has an effect on position during the H-blank period, and it only works as described when called right after a WSYNC. Read this for more info on how HSYNC works:

 

http://www.atarihq.com/danb/files/TIA_HW_Notes.txt

 

  -Bry

874432[/snapback]

That document is fantastic, and interesting, but a more practical document regarding HMOVE behavior is this one: http://www.biglist.com/lists/stella/archiv...4/msg00198.html

 

Which lists the observed behavior of hitting HMOVE at every cycle during a scanline.

[antron]

I decided to write to HMOVE on cycle 3, which is where it would have been had I called it immediately after WSYNC. Works great on the real thing too.

The tightest kernel of my game is now complete. I'll post it for critique as soon as I get it well documented.

Thanks all.

 

edit: now I have changed it to cycle 0. still no problems.

Edited September 22, 2005 by antron