[Coco] 64K Coco mode and the MC6883

[Sean Conner]

It was thus said that the Great RETRO Innovations via Coco once stated:
> On 3/26/2023 8:18 PM, Sean Conner via Coco wrote:
> >10 CLEAR 999:FOR I=1 TO 59:READ B:P$=P$+CHR$(B):NEXT I:P=VARPTR(P$)+1:POKE 
> >P,126
> >20 PRINT"HIT ANY KEY TO RUN TEST";EXEC P;PRINT
> >30 A=253:M$="ROM-1":GOSUB100
> >31 A=A+1:M$="ROM-2":GOSUB100
> >33 A=A+1:M$='ROM-3":GOSUB100
> >40 END
> >90 DATA 52,3,173,159,160,0,39
> >91 DATA 250,26,80,79,183,255,223
> >92 DATA 183,128,0,183,160,0,183
> >93 DATA 192,0,76,183,255,222,183
> >94 DATA 128,0,183,160,0,183,192
> >95 DATA 0,183,255,223,182,128,0
> >96 DATA 151,253,182,160,0,151
> >97 DATA 254,182,192,0,151,255
> >98 DATA 183,255,222,53,131
> >100 PRINT M$;": ";
> >110 IF PEEK(A)=1 THEN PRINT "NO SWITCH NEEDED" ELSE PRINT "SWITCH NEEDED"
> >120 RETURN
> 
> Hmmm, I copied that into a file, converted it to BASIC tokens with decb, 
> and then ran it in XRoar using a CoCo2 NTSC.
> 
> At first, I got a ?SN ERROR IN 20
> 
> I replaced line 20 with EXEC P and then ran again.  It then just went 
> unresponsive.

  Did you try hitting any key?  The assembly code (included in my previous
message) includes code to wait for a key press before preceeding to allow
time to get ready to trace with a scope (as you mentioned before).  I didn't
want to include such a message in the assembly code to keep it as short as
possible.  Line 20 should read:

20 PRINT"HIT ANY KEY TO RUN TEST";:EXEC P:PRINT

  -spc