4.4Timing and Frequency
4.4.1Video, Horizontal and Vertical Sync
Figure 6 illustrate video timing relationships the LC1200R operates within when the specified video mode (Table 5 Video Mode Definitions) is applied.
Front Porch defines the time from end of active video data to the start of Horiz/Vert Sync Pulse.
Back Porch defines the time from end of Horiz/Vert Sync Pulse to the start of active video data.
Blanking is the total time comprising Front Porch, Back Porch and Sync Pulse time(s).
The horizontal sync circuitry synchronizes to horizontal frequencies of 31.468 KHz ±0.5 KHz, 48.077KHz ±0.5KHz, and 56.476KHz ±0.5KHz. Horizontal sync pulse width variation is 1.813- µsec to 3.813-µsec. The LC1200R will "sync" to the specified format vertical frequencies between 60Hz and 72Hz without adjustment.
Absence of Horizontal and/or Vertical Sync will not damage the LC1200R.
4.5Video Signal On-Off Sequences
The sequence for bringing up and removal of each video input signal can be in any sequence or combination of input signals.
Table 6. Video Mode Timing Data |
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| Video Modes |
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| IBM VGA |
| VESA |
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| Resolution | 640x400 | 640x480 | 800x600 | 1024x768 |
| Video Clock | 25.175 MHz | 25.175 MHz | 50.000 MHz | 75.000 MHz |
| Horizontal Scan |
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| Freq. | 31.468 KHz | 31.468 KHz | 48.077 KHz | 56.476 KHz |
| Horizontal Line | 31.778 us 800 | 31.778 us 800 | 20.800 us 1040 | 17.707 us 1328 |
| Period | pixels | pixels | pixels | pixels |
| Horizontal | 6.356 us 160 | 6.356 us 160 | 4.800 us 240 | 4.053 um 304 |
| Blanking | pixels | pixels | pixels | pixels |
| Horizontal Sync |
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| 2.400 us 120 | 1.813 us 136 |
| Pulse | 3.813 us 96 pixels | 3.813 us 96 pixels | pixels | pixels |
| Horizontal Front |
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| Porch | 0.636 us 16 pixels | 0.636 us 16 pixels | 1.120 us 56 pixels | 0.320 us 24 pixels |
| Horizontal Back |
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| 1.920 us 144 |
| Porch | 1.907 us 48 pixels | 1.907 us 48 pixels | 1.280 us 64 pixels | pixels |
| Horizontal Active | 25.422 us 640 | 25.422 us 640 | 16.000 us 800 | 13.653 us 1024 |
| Display | pixels | pixels | pixels | pixels |
| Horizontal Sync |
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| Polarity | - | - | - | - |
| Vertical Scan Freq. | 70.087 Hz | 59.94 Hz | 72.184 Hz | 70.069 |
| Vertical Frame | 14.268 ms 449 | 16.683ms 525 | 13.853 ms 666 | 14.272 ms 806 |
| Period | lines | lines | lines | lines |
| Vertical Blanking | 1.557 ms 49 line | 1.430 ms 45 line | 1.373 ms 66 lines | 0.673 ms 38 lines |
| Vertical Sync | 0.064 ms 2 lines | 0.064 ms 2 lines | 0.125 ms 6 lines | 0.106 ms 6 lines |
LC1200R User’s Guide | 15 of 29 |