[hatari-devel] some falcon registers questions

[Miro Kropáček]

Hi,

$FFFF8006: Monitor Type BIT 7 6  (These 2 bits are duplicated in $FFFF82C0
> (BIT 1 0))
>  00 - Monochrome (SM124)
>  01 - Color (SC1224)
>  10 - VGA Color
>  11 - Television
>
True.

$FFFF8006: Memory configuration BIT 5 4
>  00 -  1Mb
>  01 -  4Mb
>  10 - 14Mb
>  11 - no boot !
>
11 is also mentioned as reserved, in all cases, not used.

$FFFF8006 is read only, the 2 monitor bits seems to be copied into
> $ffff82c0.
> But $ffff82c2 is read / write. So what happen to these 2 bits if I change
> their value while writing something to $FFFF82C2 ?
> Do they are "sticked" to their "$FFFF8006" value ?
>
I didn't try but I'd say so :) I think those bits come from hardware, i.e.
it's really no way to change them. If you insist, I can try it.

$FFFF8007 Falcon Bus Control
>    BIT 6 : F30 Start (0=Cold, 1=Warm)
>    BIT 5 : STe Bus Emulation (0=on)
>    BIT 3 : Blitter Flag (0=on, 1=off)
>    BIT 2 : Blitter (0=8mhz, 1=16mhz)
>    BIT 0 : 68030 (0=8mhz, 1=16mhz)
>
> Is this correct ?
>
Yes.

$FFFF8201/03/0d : Video Base Hi/Mi/Lo
>
> On Ste, when one writes to Hi or Mi register, low register is reset.
> Is it still true for the Falcon ?
>
Yes.

$FFFF8264.B|RW|VDL_HSH|H-Scroll Hi                          %____xxxx |F
> $FFFF8265.B|RW|VDL_HSL|H-Scroll Lo - clears Line Wide       %____xxxx
> |STE,F
>
> Some docs indicates that $FFFF8264 exists for the Falcon.
> Some other don't.
> Where is the truth ?
>
It does exist but not as shadow register but more like hi-byte (which is
unused). I.e. it's legal to write *(unsigned short*)0xffff8264 = [0-15] as
well as  *(unsigned char*)0xffff8265 = [0-15] ... however, writing to 8264
alone does something but I'm unable to tell you what. It scrolls the screen
but the picture is gambled.


All docs say that Falcon STE sound is nute, 12517 Hz, 25033 Hz, 50066 Hz
>
This is correct.


> But one doc says that Falcon STE sound is nute, 12292 Hz, 19668 Hz, 49170
> Hz
>
Bullshit, those values come from Falcon sound system, not from STE
compatibility mode.

What kind of DSP reset is done here ?
> Is it a cold reset or a warm reset ?
>
Coldest reset ever ;) It switch off DSP in hardware. Look into NoCrew's DSP
bootstrapper, there's is nice usage of this functionality.

-- 
MiKRO / Mystic Bytes
http://mikro.atari.org
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