;------------------------------; SB_DSP.ASM --; Programmer's library for the Sound Blaster DSP interface;-------------------------------                        IDEAL                        MODEL small                        DATASEGSB_IO_Port  DW 0220h    ;These values are kept here to avoid addDSP_Reset   DW 0226h    ;instructions in code that may be time-DSP_RDData  DW 022Ah    ;sensitive.DSP_Command DW 022ChDSP_RDAvail DW 022EhDSP_WRData EQU DSP_Command      ;Aliases for the same variable nameDSP_Status EQU DSP_Command                        CODESEGPUBLIC _dsp_reset,_dsp_voice,_set_SB_address,_dsp_dma_prepare,_dsp_timeMACRO await_DSPLOCAL @@Wait_Ready     push ax dx@@Wait_Ready:     mov  dx,[DSP_Status]     in   al,dx     and  al,128      jnz @@Wait_Ready     pop  dx axENDM MACROMACRO ten_microsec_delayLOCAL @@KT                 ;If you know of a better, more accurate,     push cx               ;more reliable, just plain smarter, way     mov  cx,20000         ;to do this, PLEASE TELL ME.@@KT:                      ;     nop                   ;(The idea is to kill 10 microseconds.)     loop @@KT             ;     pop  cx               ;email: heathh@cco.caltech.eduENDM ten_microsec_delay;------------------------; void far dsp_time(int pacing);-----------------------; pacing = 255 - (1,000,000 / frequency);----------------------PROC _dsp_time FARARG delay:WORD     push bp     mov  bp,sp     push ax dx     await_DSP     mov  dx,[DSP_Command]     mov  al,040h     out  dx,al     await_DSP     mov  dx,[DSP_Command]     mov  ax,[delay]     out  dx,al     pop  dx ax     pop  bp     retENDP _dsp_time;------------------------------; void far dsp_reset(void);------------------------------PROC _dsp_reset FAR     push ax dx     mov  dx,[DSP_Reset]     mov  al,1     out  dx,al     ten_microsec_delay     mov  al,0     out  dx,al@@Wait_Ready:     mov  dx,[DSP_RDAvail]     in   al,dx     and  al,128       jz @@Wait_Ready     mov  dx,[DSP_RDData]     in   al,dx     cmp  al,0AAh      jne @@Wait_Ready     mov  ax,165     push ax     call _dsp_time     pop  ax     pop  dx ax     retENDP _dsp_reset;-----------------------------; void far dsp_dma_prepare(int Dir,int Length);-----------------------------; Dir = 0 for Microphone Input, 1 for Speaker Output; Length = Length of data to be sampled/played;-----------------------------PROC _dsp_dma_prepare FARARG Dir:WORD,Len:WORD     push bp     mov  bp,sp     push ax dx     await_DSP     mov  al,24h     cmp  [Dir],0       jz @@Is_Read     mov  al,14h@@Is_Read:     mov  dx,[DSP_Command]     out  dx,al     await_DSP     mov  ax,[Len]     out  dx,al     await_DSP     mov  al,ah     out  dx,al     pop  dx ax     pop  bp     retENDP _dsp_dma_prepare;---------------------------; void far dsp_voice(Activity);---------------------------; Activity = 0 for silent, 1 for audible;---------------------------PROC _dsp_voice FARARG Which:WORD     push bp     mov  bp,sp     push dx ax     await_DSP     mov  ax,[Which]     and  al,1                  ;Want a 1/0 parameter     xor  al,1     shl  al,1     or   al,0D1h     mov  dx,[DSP_Command]     out  dx,al     pop  ax dx     pop  bp     retENDP _dsp_voice;--------------------------; void far set_SB_address(int base);-------------------------; Sets base port of SoundBlaster that other functions refer to.; Most likely value (and the default): 0x220;-------------------------PROC _set_SB_address FARARG Port:WORD     push bp     mov  bp,sp     push ax     mov  ax,[Port]     mov  [SB_IO_Port],ax     add  ax,6     mov  [DSP_Reset],ax     add  ax,4     mov  [DSP_RDData],ax     add  ax,2     mov  [DSP_Command],ax     add  ax,2     mov  [DSP_RDAvail],ax     pop  ax     pop  bp     retENDP _set_SB_addressEND