[hatari-devel] Videl code and registers

LAURENT SALLAFRANQUE laurent.sallafranque at arkea.com
Fri Mar 5 10:24:47 CET 2010


Hello,

One of the best and most complete doc about videl can be found at the following address :

http://mikro.umpc.sk/docs/mikro/videl.html

You'll find many explanitions here.

I started to have a look at this to rewrite the Videl code, but for now, I'm working on the STe microwire and LMC1992 emulation. (I'll comit soon).

I think that Videl emulation should work with a "cpuCycle" interrupt under hatari.
It would interrupt after each "halfline" to take into account correctly the "rasters" emulation and all other registers change that can happen during the screen display.

Regards,

Laurent



<--------  Eero wrote  ---------------> 

I just noticed following in Aura's Videl doc:
------------------
$FFFF82A8 [R/W] W _____A9876543210  Vertical Display Begin (VDB)

On which halfline should  begin  gfx  display.  If  VDB  >  VFT,  no display 
is present. If VDB > VDE, display is present from VDB to VFT.

$FFFF82AA [R/W] W _____A9876543210  Vertical Display End (VDE)

On which halfline should end gfx display. If  VDE < VFT, no display is 
present. If VDE < VDB, display is present from VDE to VFT.
------------------

VFT - VDB = 300 which would be fine width except that VDB < VDE.

And from what I've seen of the register values, this is always true:
	VDE < VFT,
although according to Aura's doc it would mean that no display is
present...?



Laurent Sallafranque
CICM / groupe Arkea
Domaine Ged/Archivage
1 rue Louis Lichou
29480 Le Relecq Kerhuon
Tél : 02 98 00 20 76

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