[hatari-devel] falcon crossbar and ff8932

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Hi

in falcon/crossbar.c, I see the destination device connections are 
tested using bits 13-13 in ff8932 :

        Source: D/A Convertor                 BIT 15 14 13 12
        00 - DMA output ------------------------------+--+
        01 - DSP output ------------------------------+--+
        10 - External input --------------------------+--+
        11 - ADC input -------------------------------+--'

But on the doc here 
http://www.atari-wiki.com/index.php/Atari_ST/STe/MSTe/TT/F030_Hardware_Register_Listing 
they have :

       |     |Destination: D/A Convertor            BIT 15 14 13 12|
       |     |1 - Connect, 0 - Disconnect ---------------'  |  |  ||
       |     |00 - Source DMA-PLAYBACK ---------------------+--+  ||
       |     |01 - Source DSP-XMIT -------------------------+--+  ||
       |     |10 - Source External Input -------------------+--+  ||
       |     |11 - Source A/D Convertor --------------------+--'  ||
       |     |0 - Handshake on, 1 - Handshake off ----------------'|

This would mean by setting bit 15, all sources would be disconnected 
from the D/A destination.

With current code in Hatari, it seems bit 15 is never tested, so that 
would mean something is always connected to the D/A destination.

Is that really how it works on real Falcon ? It's not possible to have 
nothing connected to the DAC destination ?

If we want to connect dma playback to DAC for example, should we write 
0xxx (bit 15=0) to ff8932 or 8xxx (bit 15=1) ?


Laurent, as you wrote code for the crossbar.c, do you have some official 
Atari documentation or some pointers to some articles that would explain 
this ?

(other possibility would be to look how tos 4 works when we call the 
system function to connect source/dest in crossbar)

Nicolas