Charles,

12MHz works for 31,250. I have a working ROM image for this board and it works fine (generates MIDI). I am trying to rewrite the code though.

I ran my code in the simulator and it seems that the TI0 interrupt was unhandled, so I added a handler.

The assembly output from the compile looks good, and matches up with tutorials I have seen...

here's the asm output:

; FUNCTION main (BEGIN)
; SOURCE LINE # 29
; SOURCE LINE # 30
; SOURCE LINE # 32
0000 C2AF CLR EAL
; SOURCE LINE # 33
0002 C2BF CLR EXEN2
; SOURCE LINE # 34
0004 C2AE CLR WDT
; SOURCE LINE # 35
0006 C2AD CLR ET2
; SOURCE LINE # 36
0008 D2AC SETB ES0
; SOURCE LINE # 37
000A C2AB CLR ET1
; SOURCE LINE # 38
000C C2AA CLR EX1
; SOURCE LINE # 39
000E C2A9 CLR ET0
; SOURCE LINE # 40
0010 C2A8 CLR EX0
; SOURCE LINE # 41
0012 D2AF SETB EAL
; SOURCE LINE # 43
0014 759850 MOV S0CON,#050H
; SOURCE LINE # 44
0017 758920 MOV TMOD,#020H
; SOURCE LINE # 45
001A 758DFF MOV TH1,#0FFH
; SOURCE LINE # 46
001D D28E SETB TR1
; SOURCE LINE # 47
001F D299 SETB TI0
; SOURCE LINE # 49
; SOURCE LINE # 50
0021 ?C0003:
; SOURCE LINE # 51
0021 3099FD JNB TI0,?C0003
0024 ?C0004:
; SOURCE LINE # 52
0024 C299 CLR TI0
; SOURCE LINE # 53
0026 7599FE MOV S0BUF,#0FEH
; SOURCE LINE # 54
0029 80F6 SJMP ?C0003

Any other help is greatly appreciated :-)

Thanks
John