This commit adds both a 480p input sampling mode and line2x optimized
mode for the PSP's 480x272 picture. The line2x optimized mode is enabled
automatically when the sampling mode is selected.
When in-game, the PSP outputs a letterboxed 480p picture. The active
portion of the screen is 480x272, but is treated as 480p (480x720).
In addition, a line2x optimized mode is added which produces a 960x544
output picture, which if desired the top + bottom pixels can be dropped
producing a 960x540 (qHD) picture.
To generate a qHD picture, use the following settings:
V. Active: 270
V. Backporch: 135
Quartus calculates fmax (the theoretical maximum clock rate) based on
the entirety of the logic between registers. In the case of the pclk_*
lines, this includes some invalid paths which cross between the
3x <-> 2x and 5x <-> 4x clock domains. This is because these clocks
share output pins from the PLL, but the PLL is configured to output only
one of these clocks at a time, and the correct output from the logic is
selected via a multiplexer. Therefore these paths cannot co-occur.
This has the effect of increasing the calculated fmax of these paths to:
pclk_3x: 107.98 MHz -> 132.52 MHz
pclk_5x: 162.23 MHz -> 170.33 MHz
Russell Harmon