Re: [video] VGA controller implementation

[Shawn Tan <shawn.tan@aeste.net>]

On Tue, 2002-07-09 at 15:34, Richard Herveille wrote:
> That's true of course. But I figured it would be a first step to a decend 
> open-source video system. There are a few around, and I subscribed to many of 
> the mailing lists. But just like this list they are kinda dead.
Yes that would be nice.. make a open-source video system that has
capabilities to be used for more functions.. maybe we can work with the
bunch of people working on a 3D accelerator too..

> I also want to provide a port for direct video access. This would allow an 
> outside source (a mpeg decoder for example) to display data. All the video 
> stuff would be handled by the vga card, the outside-source just has to 
> provide the data.
This would be really cool.. I think that you can already do this..
depending on how things are designed.. because your VGA accesses it's
video RAM from an external source, all that's needed is a block to do
the translations (assuming an external digital source).. The fact that
it accesses external VideoRAM makes it easy to read data from an outside
source.. we just need to masquerade it.. (:

> The vga card doesn't set the data-lines to zero, it presents the next pixel's 
> data. The blank signal blanks the screen. There's an intensity difference 
> between black and blank (black is less black than blank).
Ah.. So how do we get the core to send a BLACK when it reaches beyond
the 640 width?? the easiest way is to cheat and make the picture graphic
with a 1pixel black border.. hehe.. (: is there a hardware way without
modifying the core too much??

> For FPGAs I always use the VENDOR_FPGA setting. I use Leonardo Spectrum and 
> Synplicity as synthesizers/compilers. They both 'understand/recognize' the 
> structure described and generate RAM blocks for it.
Ah yes.. I guessed as much.. most people use Synplicity.. I'm using FC2
because I have access only to FC2.. it's given free with the other
Synopsys products, I think.. it's not smart enough to automagically
recognize the RAM..

with metta,
Shawn Tan.

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