;------------------------------------------------------------------------------; ; KBD_FIX.COM from Socha's Toolbox by John Socha ; ; Ref: Softalk PC Nov 83 pg 117 ; ; Softalk PC Jan 84 pg 107 (corrections, incorporated below) ; ; ; ; Note that type ahead buffer can be cleared by pressing Alt and Ctrl together.; ;------------------------------------------------------------------------------; VECTORS SEGMENT AT 0H ORG 9H*4 KEYBOARD_INT_VECTOR LABEL DWORD ORG 16H*4 KEYBOARD_IO_VECTOR LABEL DWORD VECTORS ENDS ROM_BIOS_DATA SEGMENT AT 40H ORG 17H KBD_FLG DB ? ORG 1AH ROM_BUFFER_HEAD DW ? ROM_BUFFER_TAIL DW ? KB_BUFFER DW 16 DUP (?) KB_BUFFER_END LABEL WORD ROM_BIOS_DATA ENDS CODE_SEG SEGMENT ASSUME CS:CODE_SEG ORG 100H BEGIN: JMP INIT_VECTORS ;Initialize vectors and attach to DOS ROM_KEYBOARD_INT DD ;Address for ROM routine ROM_KEYBOARD_IO DD BUFFER_HEAD DW OFFSET KEYBOARD_BUFFER BUFFER_TAIL DW OFFSET KEYBOARD_BUFFER KEYBOARD_BUFFER DW 160 DUP (0) ;159 character buffer KEYBOARD_BUFFER_END LABEL WORD ;-----------------------------------------------------------------; ; This procedure sends a short beep when the buffer fills. ; ;-----------------------------------------------------------------; KB_CONTROL EQU 61H ;Control bits for keyboard (and speaker) ERROR_BEEP PROC NEAR PUSH AX PUSH BX PUSH CX PUSHF ;Save the old interrupt enable flag CLI ;Turn off beep during interrupt MOV BX,30 ;Number of cycles for 1/8 second tone IN AL,KB_CONTROL PUSH AX START_OF_ONE_CYCLE: AND AL,0FCH OUT KB_CONTROL,AL MOV CX,60 ;Delay for one half cycle OFF_LOOP: LOOP OFF_LOOP OR AL,2 ;Turn on the speaker OUT KB_CONTROL,AL MOV CX,60 ;Delay for second half cycle ON_LOOP: LOOP ON_LOOP DEC BX ;200 cycles yet JNZ START_OF_ONE_CYCLE POP AX ;Recover old keyboard information OUT KB_CONTROL,AL POPF ;Restore interrupt flag POP CX POP BX POP AX RET ERROR_BEEP ENDP ;---------------------------------------------------------------------; ;This procedure checks the ROM keyboard buffer to see if some program ; ;tried to clear this buffer. We know it's been cleared when the ROM ; ;tail and header overlap. Normally, the new procedure below keep the ; ;dummy character, word 0, in the buffer. ; ; ; ;Uses BX,DS ; ;Writes: BUFFER_HEAD, BUFFER_TAIL, ROM_BUFFER_HEAD ; ; ROM_BUFFER_TAIL ; ;Reads: KEYBOARD_BUFFER, KB_BUFFER ; ;---------------------------------------------------------------------; CHECK_CLEAR_BUFFER PROC NEAR ASSUME DS:ROM_BIOS_DATA MOV BX,ROM_BIOS_DATA ;Establish pointer to BIOS data MOV DS,BX CLI ;Turn off interrupts during this check MOV BX,ROM_BUFFER_HEAD ;Check to see if buffer is cleared CMP BX,ROM_BUFFER_TAIL ;Is the buffer empty? JNE BUFFER_OK ;No, then everything is alright ;Yes, then clear the internal buffer MOV BX,OFFSET KB_BUFFER ;Reset the buffer with word 0 in buffer MOV ROM_BUFFER_HEAD,BX ADD BX,2 MOV ROM_BUFFER_TAIL,BX ASSUME DS:CODE_SEG MOV BX,CS MOV DS,BX MOV BX,OFFSET KEYBOARD_BUFFER ;Reset internal buffer MOV BUFFER_HEAD,BX MOV BUFFER_TAIL,BX BUFFER_OK: ASSUME DS:CODE_SEG STI ;Interrupts back on RET CHECK_CLEAR_BUFFER ENDP ;------------------------------------------------------------------------------; ;This procedure intercepts the keyboard interrupt and moves any new ; ;charcters to the internal, 80 character, buffer. ; ;------------------------------------------------------------------------------; INTERCEPT_KEYBOARD_INT PROC NEAR ASSUME DS:NOTHING PUSH DS PUSH SI PUSH BX PUSH AX CALL CHECK_CLEAR_BUFFER ;Check for buffer cleared PUSHF CALL ROM_KEYBOARD_INT ;Read scan code with BIOS routines. ;------ Transfer any charcters to internal buffer ASSUME DS:ROM_BIOS_DATA MOV BX,ROM_BIOS_DATA MOV DS,BX MOV SI,BUFFER_TAIL MOV BX,ROM_BUFFER_HEAD ;Check if real character in buffer ADD BX,2 ;Skip over dummy character CMP BX,OFFSET KB_BUFFER_END JB DONT_WRAP ;No need to wrap the pointer MOV BX,OFFSET KB_BUFFER ;Wrap the pointer DONT_WRAP: CMP BX,ROM_BUFFER_TAIL ;Is there a real character? JE NO_NEW_CHARACTERS ;No, then return to caller MOV AX,[BX] ;Yes, move character to internal buffer MOV CS:[SI],AX ADD SI,2 ;Move to next position CMP SI,OFFSET KEYBOARD_BUFFER_END JB NOT_AT_END MOV SI,OFFSET KEYBOARD_BUFFER NOT_AT_END: CMP SI,BUFFER_HEAD ;Buffer overrun? JNE WRITE_TO_BUFFER ;Yes, beef and throw out character CALL ERROR_BEEP JMP SHORT NOT_AT_KB_END WRITE_TO_BUFFER: MOV BUFFER_TAIL,SI NOT_AT_KB_END: MOV ROM_BUFFER_HEAD,BX NO_NEW_CHARACTERS: ;--------- See if CTRL + ALT pushed and clear buffer if so MOV AL,KBD_FLG ;Get status of shift keys into AL AND AL,0CH ;Isolate Alt and Ctrl shift flags CMP AL,0CH ;Are both the Ctrl and Alt keys down? JNE DONT_CLEAR_BUFFER ;No, then don't clear the buffer MOV AX,BUFFER_TAIL ;Yes, then clear the buffer MOV BUFFER_HEAD,AX DONT_CLEAR_BUFFER: POP AX POP BX POP SI POP DS IRET INTERCEPT_KEYBOARD_INT ENDP ;------------------------------------------------------------------------------; ;This procedure replaces the ROM BIOS routines for reading a character ; ;------------------------------------------------------------------------------; INTERCEPT_KEYBOARD_IO PROC FAR STI ;Interrupts back on PUSH DS ;Save current DS PUSH BX ;Save BX temporarily CALL CHECK_CLEAR_BUFFER ;Check for buffer cleared MOV BX,CS ;Establish pointer to data area MOV DS,BX OR AH,AH ;AH=0? JZ READ_CHARACTER ;Yes, read a character CMP AH,1 ;AH=1? ************** JZ READ_STATUS ;Yes, return the status POP BX ;Let the ROM BIOS handle other functions POP DS ASSUME DS:NOTHING JMP ROM_KEYBOARD_IO ;Call ROM BIOS for other functions ;Read the key ASSUME DS:CODE_SEG READ_CHARACTER: ;ASCII read STI ;Interrupts back on during loop NOP ;Allow an interrupt to occur CLI ;Interrupts back off MOV BX,BUFFER_HEAD ;Get pointer to head of buffer CMP BX,BUFFER_TAIL ;Test end of buffer JE READ_CHARACTER ;Loop until something in buffer MOV AX,[BX] ;Get scan code and ASCII code ADD BX,2 ;Move to next word in buffer CMP BX,OFFSET KEYBOARD_BUFFER_END ;At end of buffer? JNE SAVE_POINTER ;No, continue MOV BX,OFFSET KEYBOARD_BUFFER ;Yes, reset to buffer start SAVE_POINTER: MOV BUFFER_HEAD,BX ;Store value in variable POP BX POP DS IRET ;Return to caller ;------------ASCII status READ_STATUS: CLI ;Interrupts off MOV BX,BUFFER_HEAD ;Get head pointer CMP BX,BUFFER_TAIL ;If equal (ZF=1) then nothing there MOV AX,[BX] STI ;Interrupts back on POP BX ;Recover registers POP DS RET 2 ;Throw away flags INTERCEPT_KEYBOARD_IO ENDP ;------------------------------------------------------------------------------; ;This procedure initializes the interrupt vectors ; ;------------------------------------------------------------------------------; INIT_VECTORS PROC NEAR ASSUME DS:VECTORS PUSH DS ;Save old Data Segment MOV AX,VECTORS ;Set up the data segment for vectors MOV DS,AX CLI ;Don't allow interrupts MOV AX,KEYBOARD_INT_VECTOR ;Save addresses of BIOS routines MOV ROM_KEYBOARD_INT,AX MOV AX,KEYBOARD_INT_VECTOR[2] MOV ROM_KEYBOARD_INT[2],AX ;Set up new KEYBOARD_INT vector MOV KEYBOARD_INT_VECTOR,OFFSET INTERCEPT_KEYBOARD_INT MOV KEYBOARD_INT_VECTOR[2],CS STI ;Allow interrupts again ;Set up keyboard IO vector MOV AX,KEYBOARD_IO_VECTOR MOV ROM_KEYBOARD_IO,AX MOV AX,KEYBOARD_IO_VECTOR[2] MOV ROM_KEYBOARD_IO[2],AX MOV KEYBOARD_IO_VECTOR,OFFSET INTERCEPT_KEYBOARD_IO MOV KEYBOARD_IO_VECTOR[2],CS ;Now set up the keyboard buffer, etc. ASSUME DS:ROM_BIOS_DATA MOV AX,ROM_BIOS_DATA MOV DS,AX CLI ;Don't allow interrupts MOV BX,OFFSET KB_BUFFER MOV ROM_BUFFER_HEAD,BX MOV WORD PTR [BX],0 ADD BX,2 MOV ROM_BUFFER_TAIL,BX STI ;Allow interrupts again MOV DX,OFFSET INIT_VECTORS ;End of resident portion INT 27H ;Terminate but stay resident INIT_VECTORS ENDP CODE_SEG ENDS END BEGIN ¸FPšØÈéиGPšØÈéÄ‹vä¡Ò‰Dn¡Ò‰Dpö-Ót‹Dp÷؉Dp飋vä¡Ò‰Dné—‹vä¡Ò‰Dp