Video Signals And Timing: Difference between revisions
→General Timing Formula
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(Added intro to GTF) |
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The horizontal frequency should now be correct, you can decide whether or not to allow the new mode because the vertical rate has dropped below an acceptable rate, and you can inform the user that the mode is not supported.
The formula's provided by VESA use various scales of constants. Brendan's working on changing the scales to units. Right now, the scale space is still unknown.
=== GTF Using resolution and refresh rate ===
=== GTF Using resolution and pixel clock ===
=== GTF Using resolution and horizontal frequency ===
=== Variable reference ===
These are the variables used in the equations above:
==== C_PRIME ====
'''Todo''' Equals 40
==== M_PRIME ====
'''Todo''' Equals 600
==== CELL_GRAN_RND ====
Cell granularity - the amount of pixels the timings should be aligned to. For example, a VGA uses horizontal timings in multiples of the character clock, each character being 8 (graphics and some text modes) or 9 (most text modes) pixels wide. For a VGA graphics mode, you'll want to supply 8 here because of that. Depending on your specific hardware, you supply either 8 or 1.
==== MARGIN_PERCENT ====
'''Todo''' Equals 1.8
==== MIN_PORCH_RND ====
'''Todo''' Equals 1. Used to force at least one unit of blanking around the sync period in order to not confuse graphics hardware?
==== MIN_V_SYNC_AND_BACK_PORCH ====
'''Todo''' Equals 550
== Brendan's Original Posts ==
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