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Re: hbl on falcon
Posted by: Orion Apr,11.2019-13:29 

Hi dudes !

So did you come to a conclusion?

I'm facing a similar issue and I need some help from Falcon experts :)

I wrote a small program which setup the Falcon video registers in ST-compatible mode (320x200, RGB50 or VGA50 depending on the monitor type) using Leonard's init:

All CPU caches are disabled.

Then I use Timer-B in event count mode to trigger an HBL interrupt at a particular raster line.
All interrupts are disabled except Timer-B and VBL.

In the Timer-B interrupt handler, I change the background color using ST palette registers.

This simple code works perfectly on ST(e) as I get stable rasters starting from the desired raster line.

Here is what I observe on Falcon:

1) in RGB50 mode (Leornard's init), the Timer-B/HBL interrupt is triggered as expected at the start of the desired raster line.
There is an interrupt jitter: the raster is shaky on the left.
I guess that, unlike on the ST, there is "less room" to change the color before it is visible on Falcon?

2) in VGA50 mode (Leornard's init), the Timer-B/HBL interrupt is triggered in the middle of the desired raster line, and this is unexpected :)
Is it because the VIDEL uses two halflines for each raster line and the Timer-B/HBL routine is triggered on the second halfline rather than on the first one?

3) if I don't use Leonard's init to setup the video mode, but I only use the XBIOS VSetscreen() to setup the ST-compatible video mode, then I get different results
- in RGB mode, the Timer-B/HBL interrupt is triggered at the end of the previous line.
- in VGA mode, the interrupt is triggered at the start of the previous raster line, thus having the color change occurring one line earlier than expected!

So, did you progress on the understanding of VIDEL+HBL during these last 12 years ? :)

Thx for your help guys!


[All messages in this thread]

Topic Posted by  Date 
hbl on falcon mikro Sep,24.2007-16:32
  Re: hbl on falcon frost Sep,24.2007-18:08
    Re: hbl on falcon mikro Sep,25.2007-09:54
      Re: hbl on falcon earx Sep,25.2007-10:31
      Re: hbl on falcon ggn Sep,25.2007-10:36
  Re: hbl on falcon NO/Escape Sep,24.2007-20:28
  Re: hbl on falcon evil Sep,25.2007-13:55
    Re: hbl on falcon earx Sep,25.2007-16:43
    Re: hbl on falcon ggn Sep,26.2007-14:37
      Re: hbl on falcon evil Sep,26.2007-17:18
        Re: hbl on falcon mikro Sep,27.2007-09:31
        Re: hbl on falcon ggn Sep,27.2007-12:43
          Re: hbl on falcon evil Sep,27.2007-18:06
            Re: hbl on falcon ggn Sep,27.2007-21:52
  Re: hbl on falcon mikro Sep,28.2007-11:58
    Re: hbl on falcon mikro Sep,28.2007-11:59
    Re: hbl on falcon earx Sep,28.2007-14:14
      Re: hbl on falcon Mikro Sep,29.2007-17:29
        Re: hbl on falcon Mikro Sep,29.2007-19:44
          Re: hbl on falcon earx Sep,30.2007-07:18
            Re: hbl on falcon mikro Oct,01.2007-11:08
    Re: hbl on falcon ggn Oct,03.2007-08:36
      Re: hbl on falcon mikro Oct,03.2007-09:20
  Re: hbl on falcon RA/pdx Oct,15.2007-13:59
    Re: hbl on falcon mikro Oct,16.2007-09:13
      Re: hbl on falcon Orion Apr,11.2019-13:29

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