[Coco] CoCo-SDC card on a Dragon64

[Pere]

Hi,
I have written to MEM @4 in my SDC-card, a copy of a patched DosPlus50 
with an extender of mine that allows me to work with floppies as well as 
with DW4 VDK files using all of the DOS commands, it is a beta at that 
moment but works great ...

Concerning the SDC module, I have in the root of the card a STARTUP.CFG
file with these contents:
0=SDC1.DSK
1=SDC2.DSK 
to link DRIVE0 to an DSK and DRIVE1 to another

When I start my Dragon, my modified DOS shows up and I can access
the two DSK files on the card and any two DW4 slots that contain an VDK
as well.

Then I loaded the Basic program that 'should' help me to send some commands
to the SDC card, next I changed the addresses for the ones suggested in the
SDC manual, so now it looks like that:

10 OS=PEEK(&HFF7F)
20 SL=1
30 INPUT"SDC DRIVE #";DR
40 IF DR<0 OR DR>1 THEN 30
50 LINE INPUT"COMMAND?";C$
60 IF LEN(C$)<2 OR MID$(C$,2,1)<>":"THEN50
70 C$=C$+CHR$(0):P=VARPTR(C$)
80 P=PEEK(P+2)*256+PEEK(P+3)
90 'POKE&HFF7F, OS AND 240 OR SL
100 POKE&HFF48,67:POKE&HFF41,0:'ADDRESSES CONVERTED
110 POKE&HFF42,0:POKE&HFF40,DR+224:'ADDRESSES CONVERTED
120 A=&HFF42:B=&HFF43:'ADDRESSES CONVERTED
130 FOR I=P TO P+254 STEP 2:POKE A,PEEK(I):POKE B,PEEK(I+1):NEXT
140 ST=PEEK(&HFF40):IF ST AND 1 THEN 140:'ADDRESS CONVERTED
150 POKE&HFF48,0:'POKE&HFF7F,OS:'ADDRESS CONVERTED
160 IF ST AND 128 THEN PRINT "ERROR";ST

Of course in Dragon, &HFF7F is not the place to change the MPI slot
so I am not using it any more.
I forgot to tell ...
My Dragon64 has a Multi-Pak attached and I am using these slots:
slot1 --- CoCo-SDC
slot2 --- WordPak1 (not in use right now)
slot3 --- empty
slot4 --- Lafumat's disc controller with twin 3,5" floppies

Could anyone tell me what is the correct procedure that must be executed
in order to send a command like this one?
M:SDC2.DSK

When I run the Basic program and do enter that command for sdc-drive0,
I receive an OK as final message.
But if I send a DIR1, I receive the contents of the DSK initially linked to
drive0, so nothing has changed ...
I am missing somehting or I am doing more than one thing wrongly, but I
cannot spot what it is ...
Has anyone validated the addresses for the Dragon? 

Any advice would be highly appreciated

thanks in advance
regards
pere