I try to program a VGA test pattern generator and i have seen that the whole thing is divided in horizontal lines. For example the v-sync is 3 lines long.
Now i do not know how to start the horizontal line after the v-sync-line is done - this should be after the frontporch of the (next ?) v-sync.
Does the h-sync-line start with its frontporch or directly with the h-sync-signal after a vertical sync ?
The signals are generated by an AVR and the resolution is 640x480@85Hz.
There are some 3 websites with roughly the same timings for this resolution - but they seem to have a difference of 30 pixel for the start of the visible line after the horizontal back porch. This could be a flexible parameter for adjustment of the picture center on the screen.
The websites are this: martin.hinner, tinyvga and johnloomis.
I intend to start with the v-sync but do not know what part of the h-sync comes after the v-sync-line is done. Logically thought it would be a backporch of the h-sync but i am not sure because the vga-specifications seem to be not officially available.
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Excuse me i wrote it wrong. I am already a little bit further and i made a drawing of the problem. I need to know how the h-sync and the v-sync are aligned.
In the VGA timing implementations that I see, the scan line starts with VSYNC. All vertical frame events are aligned with scan line start. In so far, your "version 2" is correct.
This interpretation corresponds to the meaning of the term "backporch", it's located at the end of a scan line. But I guess the difference doesn't actually matter for proper synchronization, "version 1" would work either.