[Coco] Coco 3 pixel clock

jdaggett at gate.net jdaggett at gate.net
Tue Oct 9 10:57:14 EDT 2007

On 8 Oct 2007 at 21:01, Christopher Hawks wrote:

>  Does anyone know the pixel clock rate for the RGB output?

Not with 100% certainty.  There are few possibilities. What is most likely is 11.454545MHz 
for 640 pixel mode. This is the master clock divided by 2.5. This yields 640 pixels for display 
and 90 pixels for border and blanking interval. A total of 730 pixels. The horizontal 
frequency is 15.691 KHz in this configuration. In 320/256 pixel mode the pixel clock is the 
master clock divided by 4,  7.159090MHz. This  yields 320/256 pixels for display and 
136/200 pixels for border and blanking. Lesser resolution modes would use the color burst 

>  and if it can be programmatically changed??

Since there is only one master clock in the Coco3, the pixel clock is slaved to resolution and 
the master clock. to change pixel clock would require changing the master clock. This would 
also affect color generation if done. 

> -- 
> Christopher R. Hawks
> HAWKSoft
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