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Re: Test: the cycle

Linards Ticmanis wrote:

On 02/08/2012 10:54 PM, BLuRry wrote:



I think that I must have a timing mismatch in my code that varies by graphics mode.  But it was fun making some timing adjustments surface in the configuration (I <3 annotations!)  Just so I'm clear: HBLANK is 25 cycles long and starts at the beginning of each line, or the end of each line? Also, what is the video scanner picking up during that time?  Say that 0 is an offset relative to the leftmost byte on a row -- would it be -25, 0 or 40?  Money munchers seems to look **perfect** when I assume HBLANK starts at 0 on the current line.



You could look at the "Understandig the Apple II" book by Jim Sather,
which can be found online as a PDF. It explains the scanner in every
detail including those you asked for, at least for the old II/II+
machines. No idea whether the IIe has any marked differences here.


Note that blanking just turns off the electron beam.  The actual
vertical and horizontal retrace don't start until about halfway
through the horizontal sync pulse and the vertical sync pulses,
respectively.

So blanking starts, retrace starts, retrace completes and normal
scan begins, then blanking ends.  The relative positioning of the
sync pulse(s) within the blanking interval determines the "framing"
of the raster.

-michael

NadaNet 3.1 for Apple II parallel computing!
Home page:  http://home.comcast.net/~mjmahon/

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