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Atari coding BBS
| HBL on Falcon (follow up) |
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Posted by: Orion
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Apr,11.2019-18:59
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Hi dudes,
I'd like to follow up this old thread, http://dhs.nu/bbs-coding/index.php?request=2378, with my own experience.
(I've first posted a message to the original thread directly but as it is really old, you might miss it, so I re-post my message as a new thread).
I'm facing an issue with HBL (actually rasters) on Falcon and I need some help from the 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: http://leonard.oxg.free.fr/articles/multi_atari/multi_atari.html.
All CPU caches are disabled and CPU runs at 8MHz.
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 (with Leornard's init), the Timer-B/HBL interrupt is triggered as expected at the start of the desired raster line.
But there is an interrupt jitter: the raster is shaky on the left.
I guess that, unlike on the ST, there is "less time" to change the color before it is visible on Falcon?
2) in VGA50 mode (with 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 raster line earlier than expected!
Questions are:
- How to get the Timer-B/HBL interrupt be triggered deterministically whatever the monitor mode is used (RGB or VGA)?
- What is the recommended method to get stable rasters on Falcon?
My constraint is that I need to achieve this in ST-Compatible mode.
Thx for your help guys!
Orion/Replicants
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[All messages in this thread] [Start new thread]
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Topic
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Posted by
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Date
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HBL on Falcon (follow up)
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Orion
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Apr,11.2019-18:59
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Re: HBL on Falcon (follow up)
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Orion
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Apr,12.2019-00:30
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Re: HBL on Falcon (follow up)
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mikro
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Apr,12.2019-09:08
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Re: HBL on Falcon (follow up)
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Orion
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Apr,12.2019-11:50
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Re: HBL on Falcon (follow up)
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Daniel
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Apr,15.2019-00:09
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Re: HBL on Falcon (follow up)
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mikro
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Apr,15.2019-11:46
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Re: HBL on Falcon (follow up)
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Orion
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Apr,15.2019-15:12
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Re: HBL on Falcon (follow up)
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evil
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Apr,15.2019-11:46
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Re: HBL on Falcon (follow up)
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Orion
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Apr,15.2019-14:39
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Re: HBL on Falcon (follow up)
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mikro
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Apr,16.2019-07:43
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Re: HBL on Falcon (follow up)
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Orion
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Apr,16.2019-12:20
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Re: HBL on Falcon (follow up)
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Daniel
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Apr,16.2019-23:45
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Re: HBL on Falcon (follow up)
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mikro
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Jun,16.2019-14:26
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Re: HBL on Falcon (follow up)
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mikro
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Aug,30.2019-08:32
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