Video Timing Register
From SpecNext official Wiki
| Number | $11 |
|---|---|
| Readable | Yes |
| Writable | Yes |
| Short Description | Sets video output timing variant. |
(writable in config mode only)
| Bit | Function |
|---|---|
| 7-3 | Reserved, must be 0 |
| 2-0 | video signal timing variant |
Possible timing variants:
| Bit pattern | selected variant |
|---|---|
| %000 | Base VGA timing, clk28 = 28000000 (HDMI compatible) |
| %001 | VGA setting 1, clk28 = 28571429 (HDMI compatible) |
| %010 | VGA setting 2, clk28 = 29464286 |
| %011 | VGA setting 3, clk28 = 30000000 |
| %100 | VGA setting 4, clk28 = 31000000 |
| %101 | VGA setting 5, clk28 = 32000000 |
| %110 | VGA setting 6, clk28 = 33000000 |
Each VGA setting increases the frequency by approximately 1 kHz.
Experimental results based on "Vibrant VL5A9DL" vga monitor reports:
| mode | 50hz | 60hz |
|---|---|---|
| vga0 | 49.3 | 58.1 |
| vga1 | 50.3 | 59.3 |
| vga2 | 51.9 | 61.1 |
| vga3 | 52.8 | 62.2 |
| vga4 | 54.6 | 64.3 |
| vga5 | 56.4 | 66.4 |
| vga6 | 58.1 | 68.5 |
50/60Hz depending on bit 2 of Peripheral 1 Register ($05).