Display timing: Difference between revisions
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=Pixel dimensions= | |||
* NTSC: 384 * 264 pixels. | |||
* PAL: 384 * 312 pixels. | |||
See [[frame size]] for the '''active''' display size. | See [[frame size]] for the '''active''' display size. | ||
=Sync= | |||
'''mclk''' refers to the 24MHz master [[clock]]. A pixel lasts 4 mclk. | '''mclk''' refers to the 24MHz master [[clock]]. A pixel lasts 4 mclk. | ||
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{{Sig|BNKB|BNKB}} is the vertical blanking signal, it forces the [[video DAC]] inputs to 0. | {{Sig|BNKB|BNKB}} is the vertical blanking signal, it forces the [[video DAC]] inputs to 0. | ||
=Horizontal | ==Horizontal== | ||
[[File:Timing_video_lines.png]] | [[File:Timing_video_lines.png]] | ||
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BNKB (blanking to 0V) changes state 14px after H-sync (middle of the back porch) | BNKB (blanking to 0V) changes state 14px after H-sync (middle of the back porch) | ||
=Vertical | ==Vertical== | ||
Corrected from and added on from mvstech.txt (by Charles MacDonald). | Corrected from and added on from mvstech.txt (by Charles MacDonald). | ||
Latest revision as of 12:59, 6 February 2018
Pixel dimensions
- NTSC: 384 * 264 pixels.
- PAL: 384 * 312 pixels.
See frame size for the active display size.
Sync
mclk refers to the 24MHz master clock. A pixel lasts 4 mclk.
Notes: After /RESET goes high, SYNC goes high after 1399 mclk.
CHBL is the horizontal blanking signal, it tells NEO-B1 to output color 0 of palette 0, which is the reference color.
BNKB is the vertical blanking signal, it forces the video DAC inputs to 0.
Horizontal
- 112 mclks (28px) horizontal sync pulse
- 112 mclks (28px) back porch
- 1280 mclks (320px) active display
- 32 mclks (8px) front porch
- 32 + 112 + 112 = 256 mclks (64px) horizontal blanking
- 32 + 112 + 112 + 1280 = 1536 mclks (384px) total per scanline
BNKB (blanking to 0V) changes state 14px after H-sync (middle of the back porch)
Vertical
Corrected from and added on from mvstech.txt (by Charles MacDonald).
There are 264 scanlines per frame:
- 8 scanlines vertical sync pulse
- 16 scanlines top border (active in PAL, blanked in NTSC)
- 224 scanlines active display
- 16 scanlines bottom border (active in PAL, blanked in NTSC)
Upper 9 bits of register REG_LSPCMODE:
- $0F8~$0FF : Vertical sync (8px)
- $100~$10F : Top border (16px)
- $110~$1EF : Active display (224px)
- $1F0~$1FF : Bottom border (16px)
Frame timing
See framerate.