Rasters: Difference between revisions
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When programming, the raster is often referred to as the act of modifying the setting of inks between 2 scanlines, in interrupt mode. | |||
This is a way to display more than the usual [[Video modes]] number of colours. | This is a way to display more than the usual [[Video modes]] number of colours. | ||
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The time between the display of 2 Scanlines by the CRTC allow the CPU to order the Gate array to modify the setting of inks. | The time between the display of 2 Scanlines by the CRTC allow the CPU to order the Gate array to modify the setting of inks. | ||
The screen | The screen is updated with a frequency of 50Hz...The [[CPU]] ([[Z80]]) runs at about 4 MHz. | ||
So It has enough cycles between 2 scanlines to order this. | So It has enough cycles between 2 scanlines to order this. | ||
You can also use Split raster to "actually" display 2 different screens, sometimes with different Video Modes. This also allows a Graphic heavy [[HUD]] with no interference with [[Scrolling]]. | You can also use Split raster to "actually" display 2 different screens, sometimes with different Video Modes. This also allows a Graphic heavy [[HUD]] with no interference with [[Scrolling]]. | ||
==Links== | ==Links== | ||
*[http://en.wikipedia.org/wiki/Raster Wikipedia link to Raster concepts] | *[http://en.wikipedia.org/wiki/Raster Wikipedia link to Raster concepts] | ||
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*[[Synchronising with the CRTC and display]] | *[[Synchronising with the CRTC and display]] | ||
*[[Programming:Simple Raster Example 1]] | *[[Programming:Simple Raster Example 1]] | ||
Revision as of 08:27, 14 October 2009
When programming, the raster is often referred to as the act of modifying the setting of inks between 2 scanlines, in interrupt mode.
This is a way to display more than the usual Video modes number of colours.
The time between the display of 2 Scanlines by the CRTC allow the CPU to order the Gate array to modify the setting of inks.
The screen is updated with a frequency of 50Hz...The CPU (Z80) runs at about 4 MHz.
So It has enough cycles between 2 scanlines to order this.
You can also use Split raster to "actually" display 2 different screens, sometimes with different Video Modes. This also allows a Graphic heavy HUD with no interference with Scrolling.
Links
CPCWiki Links