Amiga native / RTG selection

[alexh]

This is really a direct question for Mastatabs, but I thought that I'd throw it out to the general public incase someone else knows.

How does the Picasso IV (or any other RTG card with integrated automon) determine when to switch between RTG and Amiga native?

Is it software, through a driver?

Or more likely hardware, perhaps simple chroma keying? i.e. Sample pixels of the native output over several frames and if they are not always colour X switch to native? (I guess if it were that simple the side effects would have been seen by now)

Just curious for a minimig related enhancement.

[MastaTabs]

For the PicassoIV it's software.

At first the PIV's Firmware, the PicassoIV.resource, is setting up the Cirrus chip and the cards framebuffer.
The hardware is detecting the Amigas output and the mode it is in. The Firmware reads these values and is setting the corresponding screen mode in the Cirrus CRTC registers. Then it enables the Cirrus capture port that reads the reformated digital Amiga signal directly into the currently shown framebuffer. Thats about it.

Later on Picasso96's PIV driver takes control over the native Screenmode handling through the PIV using the PicassoIV.resource.

I don't really know the procedure for other Amiga graphic cards cause the PIV is a bit special here. But I believe for them it is software controled too.

regs
MastaTabs