;Set of keyboard routines with sound outputs
.MODEL small
.STACK 500
.DATA
  ;define table for sound output
;sample_sounds      dw   8,45000   ;long low sound
;              dw   2,2000         ;short high sound
;              dw   0              ;end of sample sound table

sound_table    dw   0
sound_time_m   dw   0
sound_time_l   dw   0
sound_flag     db   0
sound_on_flag  db   0,0
key_time_out_m dw   0
key_time_out_l dw   0

.CODE
;************  ^^^^^^^^^^  *************
;### code entry point #####
get_keyinput   proc near
;this routine checks for keyboard data in BIOS buffer
 ; and returns with data if there
;else it updates sound output data and loops to check for
 ; keyboard data again until keyboard data found
;on exit AX has keyboard data
     public    get_keyinput
     push bx
     push cx
     push dx
get_keyinput_loop:
          mov  ah,1   ;set AH for scan
          int  16H    ;BIOS Call
           ;branch if no keyboard data
          jz   sound_update
          mov  ah,0   ;set AH for get key
          int  16H    ;BIOS Call
     pop  dx
     pop  cx
     pop  bx
     ret
;*******  -------- *******
sound_update:
     cmp  sound_flag,0        ;check for sound on????
     jz   get_keyinput_loop   ;branch out if sound off
     mov  cx,sound_time_m     ;else check for sound update
     mov  ax,sound_time_l
     call test_current_time   ;is it time for update ??
     jc   get_keyinput_loop   ;branch if not time
     mov  bx,sound_table
     mov  ax,[bx]             ;get next sound update value
     or   ax,ax               ;?? end of sound ??
     jz   turn_sound_off      ;branch if end sound
     call get_time_plus_ax    ;reset sound duration
     mov  sound_time_m,cx
     mov  sound_time_l,ax
     inc  bx
     inc  bx
     mov  ax,[bx]
     inc  bx
     inc  bx
     mov  sound_table,bx
     call sound_out_ax       ;go set sound frequency
     jmp  get_keyinput_loop  ;branch to keyboard loop
turn_sound_off:
     call sound_off
     mov  sound_flag,0
     jmp  get_keyinput_loop  ;branch to keyboard loop
get_keyinput   endp
;^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
;************ ########## *************
;### code entry point #####
get_keyinput_to     proc near
;get keyboard data with timeout if no data available
;on entry AX has time duration in 18 ticks per second
;on exit if carry clear then AX has keyboard data
     public    get_keyinput_to
     push bx
     push cx
     push dx
     call get_time_plus_ax     ;add duration to current time
     mov  key_time_out_m,cx    ;set timeout value
     mov  key_time_out_l,ax
get_keyinput_to_loop:
     mov  ah,1                ;ready to scan keyboard data
     int  16H                 ;BIOS Call
     jz   sound_update_to     ;branch if no keyboard data
     mov  ah,0                ;ready to get key data
     int  16H                   ;BIOS Call
     pop  dx
     pop  cx
     pop  bx
     clc                        ;set keyboard data flag
     ret
get_keyinput_to_1:
     mov  cx,key_time_out_m     ;check for timeout
     mov  ax,key_time_out_l
     call test_current_time
     jc   get_keyinput_to_loop  ;branch if no timeout
     xor  ax,ax                 ;else timeout return condition
     pop  dx
     pop  cx
     pop  bx
     stc                        ;set no keyboard data flag
     ret
; ********  %%%%%%%  ********
sound_update_to:
     cmp  sound_flag,0        ;check for sound on????
     jz   get_keyinput_to_1   ;branch if sound off
     mov  cx,sound_time_m     ;else check for sound update
     mov  ax,sound_time_l
     call test_current_time
     jc   get_keyinput_to_1   ;branch if not ready for update
     mov  bx,sound_table
     mov  ax,[bx]
     or   ax,ax               ;test for end of table
     jz   turn_sound_off_to   ;branch if end of table data
     call get_time_plus_ax
     mov  sound_time_m,cx
     mov  sound_time_l,ax
     inc  bx
     inc  bx
     mov  ax,[bx]
     inc  bx
     inc  bx
     mov  sound_table,bx
     call sound_out_ax
     jmp  get_keyinput_to_1
turn_sound_off_to:
     call sound_off
     mov  sound_flag,0
     jmp  get_keyinput_to_1
get_keyinput_to     endp
;^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
;************  @@@@@@@@@@  ************
;### code entry point #####
start_table_sound   proc near
 ;subroutine to start background sound output
 ;on entry BX indexes sound data table
     public    start_table_sound
     push ax
     push bx
     mov  ax,[bx]
     call get_time_plus_ax
     mov  sound_time_m,cx
     mov  sound_time_l,ax
     inc  bx
     inc  bx
     mov  ax,[bx]
     inc  bx
     inc  bx
     mov  sound_table,bx
     call sound_out_ax
     mov  sound_flag,0FFH
     pop  bx
     pop  ax
     ret
start_table_sound   endp

;************  ==========  *************
;### code entry point #####
flush_keyboard proc near
  ;utility to flush contents of keyboard buffer
     public    flush_keyboard
     mov  ah,1
     int  16H       ;BIOS Call  ;scan for keyboard data
     jz   flush_keyboard_x      ;branch if no keyboard data
     mov  ah,0                  ;else get keyboard data
     int  16H       ;BIOS Call
     jmp  flush_keyboard
flush_keyboard_x:
     ret
flush_keyboard endp

;*************  -----------  **************
sound_out_ax   proc near
  ;set sound out frequency to data value in AX
     push ax
     push ax
     cmp  sound_on_flag,0
     jne  sound_out_1
     in   al,61H         ;input port 61h
     or   al,3
     out  61H,al         ;output port 61h
sound_out_1:
     mov  al,0B6H
     out  43H,al         ;output port 43h
     pop  ax
     out  42H,al         ;output port 42h
     xchg al,ah
     out  42H,al         ;output port 42h
     mov  sound_on_flag,0FFH
     pop  ax
     ret
sound_out_ax   endp

;***********  $$$$$$$$$$  ************
;###### code entry point #######
sound_off proc near
   ;turn sound port off
     public    sound_off
     push ax
     cmp  sound_on_flag,0
     je   sound_off_exit
     in   al,61H         ;input port 61h
     and  al,0FCH
     out  61H,al         ;output port 61h
     mov  sound_on_flag,0
sound_off_exit:
     pop  ax
     ret
sound_off endp

;**************  %%%%%%%%%%  ***************
;with all CX:AX time values, CX is most significant
 ; and AX is least significant
get_current_time    proc near
;on exit CX:AX has 32 bit day clock value
 ; in 18.2 ticks per second
     push dx
          xor  ax,ax     ;set AH to zero
          int  1AH       ;BIOS Call get time
          mov  ax,dx
     pop  dx
     ret
get_current_time    endp

;****************************
get_time_plus_ax    proc near
;on entry AX has 16 bit value to add to current clock time
;on exit CX:AX has new 32 bit clock value
     push dx
     push ax
     xor  ax,ax
     int  1AH            ;BIOS Call
     pop  ax
     add  ax,dx
     adc  cx,0
     pop  dx
     ret
get_time_plus_ax    endp

;************  ########  ************
test_current_time   proc near
;on entry CX:AX has time value
 ; to be subtracted from the current time
;on exit if carry set then current time
 ; is less than CX:AX time
     push dx
     push cx
     push ax
     xor  ax,ax
     int  1AH            ;BIOS Call
     cmp  dx,18
     jb   test_current_time_2
test_current_time_1:
     pop  ax
     sub  dx,ax
     pop  dx
     sbb  cx,dx
     mov  cx,dx
     pop  dx
     ret
test_current_time_2:
     or   cx,cx
     jnz  test_current_time_1
     pop  ax      ;this is fix code for midnight factor
     pop  dx
     pop  dx
     clc          ;clear carry condition
     ret
test_current_time   endp
;*****************************************
     end