mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-24 20:35:25 +00:00
484 lines
22 KiB
NASM
484 lines
22 KiB
NASM
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VECTORS SEGMENT AT 0H ;Set up segment to intercept Interrupts
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ORG 9H*4 ;The keyboard Interrupt
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KEYBOARD_INT LABEL DWORD
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ORG 1CH*4 ;Timer Interrupt
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TIMER_VECTOR LABEL DWORD
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VECTORS ENDS
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SCREEN SEGMENT AT 0B000H ;A dummy segment to use as the
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SCREEN ENDS ;Extra Segment
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ROM_BIOS_DATA SEGMENT AT 40H ;BIOS statuses held here, also keyboard buffer
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ORG 1AH
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HEAD DW ? ;Unread chars go from Head to Tail
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TAIL DW ?
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BUFFER DW 16 DUP (?) ;The buffer itself
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BUFFER_END LABEL WORD
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ROM_BIOS_DATA ENDS
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CODE_SEG SEGMENT
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ASSUME CS:CODE_SEG
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ORG 100H ;ORG = 100H to make this into a .COM file
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FIRST: JMP LOAD_KEEPER ;First time through
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COPY_RIGHT DB '(C)1985 S.HOLZNER' ;Ascii autograph
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PAD DB 20*102 DUP(0) ;Memory storage for pad
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PAD_CURSOR DW 9*102 ;Current position in pad
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ATTRIBUTE DB 112 ;Pad Attribute -- reverse video
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LINE_ATTRIBUTE DB 240 ;Flashing Rev video
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OLD_ATTRIBUTE DB 7 ;Original screen attrib: normal
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PAD_OFFSET DW 0 ;Chooses 1st 250 bytes or 2nd
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FIRST_POSITION DW ? ;Position of 1st char on screen
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TRIGGER_FLAG DW 0 ;Trigger on or off
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FULL_FLAG DB 0 ;Buffer Full Flag
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LINE DW 9 ;Line number, 0-9
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SCREEN_SEG_OFFSET DW 0 ;0 for mono, 8000H for graphics
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IO_CHAR DW ? ;Holds addr of Put or Get_Char
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STATUS_PORT DW ? ;Video controller status port
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OLD_KEYBOARD_INT DD ? ;Location of old kbd interrupt
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FINISHED_FLAG DB 1 ;If not finished,f buffer
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COMMAND_INDEX DW 1 ;Stores positior timer)
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ROM_TIMER DD 1 ;The Timer interrupt's address
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OLD_HEAD DW 0
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KEEPER PROC NEAR ;The keyboard interrupt will now come here.
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ASSUME CS:CODE_SEG
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PUSH AX ;Save the used registers for good form
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PUSH BX
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PUSH CX
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PUSH DX
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PUSH DI
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PUSH SI
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PUSH DS
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PUSH ES
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PUSHF ;First, call old keyboard interrupt
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CALL OLD_KEYBOARD_INT
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ASSUME DS:ROM_BIOS_DATA ;Examine the char just put in
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MOV BX,ROM_BIOS_DATA
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MOV DS,BX
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MOV BX,TAIL ;Point to current tail
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CMP BX,HEAD ;If at head, kbd int has deleted char
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JE BYE ;So leave
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MOV DX,HEAD
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SUB DX,2 ;Point to just read in character
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CMP DX,OFFSET BUFFER ;Did we undershoot buffer?
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JAE NOWRAP ;Nope
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MOV DX,OFFSET BUFFER_END ;Yes -- move to buffer top
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SUB DX,2 ;Compare two bytes back from head
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NOWRAP: CMP DX,TAIL ;If it's the tail, buffer is full
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JNE NOTFULL ;We're OK, jump to NotFull
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CMP FULL_FLAG,1 ;Check if keyboard buffer full
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JE BYE ;Yep, leave
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MOV FULL_FLAG,1 ;Oops, full, set flag and take
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JMP CHK ; this last character
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NOTFULL:MOV FULL_FLAG,0 ;Always reset Full_Flag when buff clears
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CHK: CMP TRIGGER_FLAG,0 ;Is the window on (triggered?)
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JNE SUBT ;Yep, keep going
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MOV DX,OLD_HEAD ;Check position of buffer head
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CMP DX,HEAD
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JNE CONT
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MOV OLD_HEAD,0
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BYE: JMP OUT
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CONT: MOV DX,HEAD
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MOV OLD_HEAD,DX
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SUBT: SUB BX,2 ;Point to just read in character
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CMP BX,OFFSET BUFFER ;Did we undershoot buffer?
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JAE NO_WRAP ;Nope
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MOV BX,OFFSET BUFFER_END ;Yes -- move to buffer top
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SUB BX,2 ;
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NO_WRAP:MOV DX,[BX] ;Char in DX now
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;------ CHAR IN DX NOW -------
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CMP FINISHED_FLAG,0
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JE IN
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CMP DX,310EH ;Default trigger is a ^N here.
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JNE NOT_TRIGGER ;No
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MOV TAIL,BX
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NOT TRIGGER_FLAG ;Switch Modes
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CMP TRIGGER_FLAG,0 ;Trigger off?
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JNE TRIGGER_ON ;No, only other choice is on
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TRIGGER_OFF:
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MOV OLD_HEAD,0 ;Reset old head
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MOV AH,OLD_ATTRIBUTE ;Get ready to restore screen
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MOV ATTRIBUTE,AH ;Pad and blinking line set to orig.
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MOV LINE_ATTRIBUTE,AH ; values
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MOV PAD_OFFSET,10*102 ;Point to 2nd half of pad
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LEA AX,PUT_CHAR ;Make IO call Put_Char as it scans
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MOV IO_CHAR,AX ;over all locations in pad on screen
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CALL IO ;Restore screen
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CMP LINE,9 ;Was the window turned off without
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JE IN ; using up-down keys? If so, exit
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MOV AX,LINE ;No, there is a line to stuff in
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MOV CL,102 ; keyboard buffer
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MUL CL ;Find its location in Pad
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MOV COMMAND_INDEX,AX ;And send to Put
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CALL PUT ;Which will do actual stuffing
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IN: JMP OUT ;Done
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TRIGGER_ON: ;Window just turned on
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MOV LINE,9 ;Set blinking line to bottom
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MOV PAD_OFFSET,10*102 ;Point to screen storage part of pad
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LEA AX,GET_CHAR ;Make IO use Get_char so current screen
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MOV IO_CHAR,AX ;is stored
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CALL IO ;Store Screen
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CALL DISPLAY ;And put up the pad
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JMP OUT ;Done here.
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NOT_TRIGGER:
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TEST TRIGGER_FLAG,1 ;Is Trigger on?
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JZ RUBOUT_TEST
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MOV TAIL,BX ;Yes, delete this char from buffer
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UP: CMP DX,4800H ;An Up cursor key?
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JNE DOWN ;No, try Down
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DEC LINE ;Move blinker up one line
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CMP LINE,0 ;At top? If so, reset
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JGE NOT_TOP
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MOV LINE,9
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NOT_TOP:CALL DISPLAY ;Display result
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JMP OUT ;And leave
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DOWN: CMP DX,5000H ;Perhaps Down cusor key pushed
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JNE IN ;If not, ignore key
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INC LINE ;If so, move down one
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CMP LINE,9 ;If at bottom, wrap to top
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JLE NOT_BOT
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MOV LINE,0
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NOT_BOT:CALL DISPLAY ;Show results
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JMP OUT ;And exit
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RUBOUT_TEST:
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CMP DX,0E08H ;Is it a Rubout?
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JNE CHAR_TEST ;No -- try carriage return-line feed
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MOV BX,PAD_CURSOR ;Yes -- get current pad location
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CMP BX,9*102 ;Are we at beginning of last line?
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JLE NEVER_MIND ;Yes -- can't rubout past beginning
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SUB PAD_CURSOR,2 ;No, rubout this char
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MOV PAD[BX-2],20H ;Move a space in instead (3920H)
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MOV PAD[BX-1],39H
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NEVER_MIND:
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JMP OUT ;Done here.
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CHAR_TEST:
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CMP DL,13 ;Is this a carriage return?
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JE PLUG ;If yes, plug this line into Pad
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CMP DL,32 ;If this char < Ascii 32, delete line
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JGE PLUG
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MOV PAD_CURSOR,9*102 ;Clear the current line
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MOV CX,51
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MOV BX,9*102
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CLEAR: MOV WORD PTR PAD[BX],0
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ADD BX,2
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LOOP CLEAR
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JMP OUT ;And exit
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PLUG: MOV BX,PAD_CURSOR ;Get current pad location
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CMP BX,10*102-2 ;Are we past the end of the pad?
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JGE CRLF_TEST ;Yes -- throw away char
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MOV WORD PTR PAD[BX],DX ;No -- move ASCII code into pad
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ADD PAD_CURSOR,2 ;Increment pad location
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CRLF_TEST:
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CMP DX,1C0DH ;Is it a carriage return-line feed?
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JNE OUT ;No -- put it in the pad
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CALL CRLF ;Yes -- move everything up in pad
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OUT: POP ES ;Having done Pushes, here are the Pops
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POP DS
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POP SI
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POP DI
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POP DX
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POP CX
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POP BX
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POP AX
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IRET ;An interrupt needs an IRET
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KEEPER ENDP
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DISPLAY PROC NEAR ;Puts the whole pad on the screen
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PUSH AX
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MOV ATTRIBUTE,112 ;Use reverse video
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MOV LINE_ATTRIBUTE,240
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MOV PAD_OFFSET,0 ;Use 1st 250 bytes of pad memory
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LEA AX,PUT_CHAR ;Make IO use Put-Char so it does
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MOV IO_CHAR,AX
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CALL IO ;Put result on screen
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POP AX
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RET ;Leave
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DISPLAY ENDP
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CRLF PROC NEAR ;This handles carriage returns
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PUSH BX ;Push everything conceivable
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PUSH CX
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PUSH DI
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PUSH SI
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PUSH DS
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PUSH ES
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ASSUME DS:CODE_SEG ;Set DS to Code_Seg here
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PUSH CS
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POP DS
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ASSUME ES:CODE_SEG ;And ES too
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PUSH DS
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POP ES
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LEA DI,PAD ;Get ready to move contents of Pad
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MOV SI,DI ; up one line
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ADD SI,102 ;DI-top line, SI-one below top line
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MOV CX,9*51
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MOV BX,PAD_CURSOR ;But first finish line with a 0
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CMP BX,9*102+2 ; as a flag letting Put know line is
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JE POPS ; done.
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MOV WORD PTR PAD[BX],0
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REP MOVSW ;Move up Pad contents
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MOV CX,51 ;Now fill the last line with spaces
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MOV AX,3920H
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REP STOSW ;Using Stosw
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POPS: MOV PAD_CURSOR,9*102 ;And finally reset Cursor to beginning
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POP ES ; of the last line again.
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POP DS
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POP SI
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POP DI
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POP CX
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POP BX
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DONE: RET ;And out.
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CRLF ENDP
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GET_CHAR PROC NEAR ;Gets a char from screen and advances position
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ASSUME ES:SCREEN,DS:ROM_BIOS_DATA
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PUSH DX
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MOV SI,2 ;Loop twice, once for char, once for attribute
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MOV DX,STATUS_PORT ;Get ready to read video controller status
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G_WAIT_LOW: ;Start waiting for a new horizontal scan -
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IN AL,DX ;Make sure the video controller scan status
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TEST AL,1 ;is low
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JNZ G_WAIT_LOW
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G_WAIT_HIGH: ;After port has gone low, it must go high
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IN AL,DX ;before it is safe to read directly from
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TEST AL,1 ;the screen buffer in memory
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JZ G_WAIT_HIGH
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MOV AH,ES:[DI] ;Do the move from the screen, one byte at a time
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INC DI ;Move to next screen location
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DEC SI ;Decrement loop counter
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CMP SI,0 ;Are we done?
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JE LEAVE ;Yes
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MOV PAD[BX],AH ;No -- put char we got into the pad
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JMP G_WAIT_LOW ;Do it again
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LEAVE: MOV OLD_ATTRIBUTE,AH
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ADD BX,2
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POP DX
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RET
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GET_CHAR ENDP
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PUT_CHAR PROC NEAR ;Puts one char on screen and advances position
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PUSH DX
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MOV AH,PAD[BX] ;Get the char to be put onto the screen
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CMP AH,32
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JAE GO
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MOV AH,32
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GO: MOV SI,2 ;Loop twice, once for char, once for attribute
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MOV DX,STATUS_PORT ;Get ready to read video controller status
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P_WAIT_LOW: ;Start waiting for a new horizontal scan -
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IN AL,DX ;Make sure the video controller scan status
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TEST AL,1 ;is low
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JNZ P_WAIT_LOW
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P_WAIT_HIGH: ;After port has gone low, it must go high
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IN AL,DX ;before it is safe to write directly to
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TEST AL,1 ;the screen buffer in memory
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JZ P_WAIT_HIGH
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MOV ES:[DI],AH ;Move to screen, one byte at a time
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MOV AH,ATTRIBUTE ;Load attribute byte for second pass
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INC DI ;Point to next screen postion
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DEC SI ;Decrement loop counter
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JNZ P_WAIT_LOW ;If not zero, do it one more time
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ADD BX,2
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POP DX
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RET ;Exeunt
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PUT_CHAR ENDP
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IO PROC NEAR ;This scans over all screen positions of the pad
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ASSUME ES:SCREEN ;Use screen as extra segment
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MOV BX,SCREEN
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MOV ES,BX
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PUSH DS
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MOV BX,ROM_BIOS_DATA
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MOV DS,BX
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MOV BX,4AH
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MOV BX,DS:[BX]
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SUB BX,51
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ADD BX,BX
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MOV FIRST_POSITION,BX
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POP DS
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MOV DI,SCREEN_SEG_OFFSET ;DI will be pointer to screen postion
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ADD DI,FIRST_POSITION ;Add width of screen minus pad width
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MOV BX,PAD_OFFSET ;BX will be pad location pointer
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MOV CX,10 ;There will be 10 lines
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LINE_LOOP:
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PUSH WORD PTR ATTRIBUTE
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PUSH CX ;Figure out whether this is blinking
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NEG CX ; line and if so, temporarily change
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ADD CX,10 ; display attribute
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CMP CX,LINE
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JNE NOLINE
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MOV CL,LINE_ATTRIBUTE
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MOV ATTRIBUTE,CL
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NOLINE: POP CX
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MOV DX,51 ;And 51 spaces across
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CHAR_LOOP:
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CALL IO_CHAR ;Call Put-Char or Get-Char
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DEC DX ;Decrement character loop counter
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JNZ CHAR_LOOP ;If not zero, scan over next character
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ADD DI,FIRST_POSITION ;Add width of screen minus pad width
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POP WORD PTR ATTRIBUTE
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LOOP LINE_LOOP ;And now go back to do next line
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RET ;Finished
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IO ENDP
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PUT PROC NEAR ;Here it is.
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ASSUME DS:ROM_BIOS_DATA ;Free DS
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PUSH DS ;Save all used registers
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PUSH SI
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PUSH DI
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PUSH DX
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PUSH CX
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PUSH BX
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PUSH AX
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MOV AX,ROM_BIOS_DATA ;Just to make sure
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MOV DS,AX ;Set DS correctly
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FIN: MOV FINISHED_FLAG,1 ;Assume we'll finish
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MOV BX,TAIL ;Prepare to move to buffer's tail
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MOV SI,COMMAND_INDEX ;Get our source index
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STUFF: MOV AX,WORD PTR PAD[SI]
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ADD SI,2 ;Point to the command's next character
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CMP AX,0 ;Is it a zero? (End of command)
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JE NO_NEW_CHARACTERS ;Yes, leave with Finished_Flag=1
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MOV DX,BX ;Find position in buffer from BX
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||
|
|
ADD DX,2 ;Move to next position for this word
|
||
|
|
CMP DX,OFFSET BUFFER_END ;Are we past the end?
|
||
|
|
JL NO_WRAP2 ;No, don't wrap
|
||
|
|
MOV DX,OFFSET BUFFER ;Wrap
|
||
|
|
NO_WRAP2:
|
||
|
|
CMP DX,HEAD ;Buffer full but not yet done?
|
||
|
|
JE BUFFER_FULL ;Time to leave, set Finished_Flag=0.
|
||
|
|
ADD COMMAND_INDEX,2 ;Move to next word in command
|
||
|
|
MOV [BX],AX ;Put it into the buffer right here.
|
||
|
|
ADD BX,2 ;Point to next space in buffer
|
||
|
|
CMP BX,OFFSET BUFFER_END ;Wrap here?
|
||
|
|
JL NO_WRAP3 ;No, readjust buffer tail
|
||
|
|
MOV BX,OFFSET BUFFER ;Yes, wrap
|
||
|
|
NO_WRAP3:
|
||
|
|
MOV TAIL,BX ;Reset buffer tail
|
||
|
|
JMP STUFF ;Back to stuff in another character.
|
||
|
|
BUFFER_FULL: ;If buffer is full, let timer take over
|
||
|
|
MOV FINISHED_FLAG,0 ; by setting Finished_Flag to 0.
|
||
|
|
NO_NEW_CHARACTERS:
|
||
|
|
POP AX ;Restore everything before departure.
|
||
|
|
POP BX
|
||
|
|
POP CX
|
||
|
|
POP DX
|
||
|
|
POP DI
|
||
|
|
POP SI
|
||
|
|
POP DS
|
||
|
|
STI
|
||
|
|
RET
|
||
|
|
PUT ENDP
|
||
|
|
|
||
|
|
ASSUME DS:CODE_SEG
|
||
|
|
INTERCEPT_TIMER PROC NEAR ;This completes filling the buffer
|
||
|
|
PUSHF ;Store used flags
|
||
|
|
PUSH DS ;Save DS since we'll change it
|
||
|
|
PUSH CS ;Put current value of CS into DS
|
||
|
|
POP DS
|
||
|
|
CALL ROM_TIMER ;Make obligatory call
|
||
|
|
PUSHF
|
||
|
|
CMP FINISHED_FLAG,1 ;Do we have to do anything?
|
||
|
|
JE OUT1 ;No, leave
|
||
|
|
CLI ;Yes, start by clearing interrupts
|
||
|
|
PUSH DS ;Save these.
|
||
|
|
PUSH SI
|
||
|
|
PUSH DX
|
||
|
|
PUSH BX
|
||
|
|
PUSH AX
|
||
|
|
ASSUME DS:ROM_BIOS_DATA ;Point to the keyboard buffer again.
|
||
|
|
MOV AX,ROM_BIOS_DATA
|
||
|
|
MOV DS,AX
|
||
|
|
MOV BX,TAIL ;Prepare to put characters in at tail
|
||
|
|
MOV FINISHED_FLAG,1 ;Assume we'll finish
|
||
|
|
MOV SI,COMMAND_INDEX ;Find where we left ourselves
|
||
|
|
|
||
|
|
STUFF2: MOV AX,WORD PTR PAD[SI] ;The same stuff loop as above.
|
||
|
|
ADD SI,2 ;Point to next command character.
|
||
|
|
CMP AX,0 ;Is it zero? (end of command)
|
||
|
|
JNE OVER ;No, continue.
|
||
|
|
JMP NO_NEW_CHARACTERS2 ;Yes, leave with Finished_Flag=1
|
||
|
|
OVER: MOV DX,BX ;Find position in buffer from BX
|
||
|
|
ADD DX,2 ;Move to next position for this word
|
||
|
|
CMP DX,OFFSET BUFFER_END ;Are we past the end?
|
||
|
|
JL NO_WRAP4 ;No, don't wrap
|
||
|
|
MOV DX,OFFSET BUFFER ;Do the Wrap rap.
|
||
|
|
NO_WRAP4:
|
||
|
|
CMP DX,HEAD ;Buffer full but not yet done?
|
||
|
|
JE BUFFER_FULL2 ;Time to leave, come back later.
|
||
|
|
ADD COMMAND_INDEX,2 ;Point to next word of command.
|
||
|
|
MOV [BX],AX ;Put into buffer
|
||
|
|
ADD BX,2 ;Point to next space in buffer
|
||
|
|
CMP BX,OFFSET BUFFER_END ;Wrap here?
|
||
|
|
JL NO_WRAP5 ;No, readjust buffer tail
|
||
|
|
MOV BX,OFFSET BUFFER ;Yes, wrap
|
||
|
|
NO_WRAP5:
|
||
|
|
MOV TAIL,BX ;Reset buffer tail
|
||
|
|
JMP STUFF2 ;Back to stuff in another character
|
||
|
|
BUFFER_FULL2:
|
||
|
|
MOV FINISHED_FLAG,0 ;Set flag to not-done-yet.
|
||
|
|
NO_NEW_CHARACTERS2:
|
||
|
|
POP AX ;Restore these.
|
||
|
|
POP BX
|
||
|
|
POP DX
|
||
|
|
POP SI
|
||
|
|
POP DS
|
||
|
|
OUT1: POPF ;And Exit.
|
||
|
|
POP DS
|
||
|
|
IRET ;With customary IRET
|
||
|
|
INTERCEPT_TIMER ENDP
|
||
|
|
|
||
|
|
LOAD_KEEPER PROC NEAR ;This procedure intializes everything
|
||
|
|
ASSUME DS:VECTORS ;The data segment will be the Interrupt area
|
||
|
|
MOV AX,VECTORS
|
||
|
|
MOV DS,AX
|
||
|
|
|
||
|
|
MOV AX,KEYBOARD_INT ;Get the old interrupt service routine
|
||
|
|
MOV OLD_KEYBOARD_INT,AX ;address and put it into our location
|
||
|
|
MOV AX,KEYBOARD_INT[2] ;OLD_KEYBOARD_INT so we can call it.
|
||
|
|
MOV OLD_KEYBOARD_INT[2],AX
|
||
|
|
|
||
|
|
MOV KEYBOARD_INT,OFFSET KEEPER ;Now load the address of our notepad
|
||
|
|
MOV KEYBOARD_INT[2],CS ;routine into the keyboard interrupt
|
||
|
|
|
||
|
|
MOV AX,TIMER_VECTOR ;Now same for timer
|
||
|
|
MOV ROM_TIMER,AX
|
||
|
|
MOV AX,TIMER_VECTOR[2]
|
||
|
|
MOV ROM_TIMER[2],AX
|
||
|
|
|
||
|
|
MOV TIMER_VECTOR,OFFSET INTERCEPT_TIMER
|
||
|
|
MOV TIMER_VECTOR[2],CS ;And intercept that too.
|
||
|
|
|
||
|
|
ASSUME DS:ROM_BIOS_DATA
|
||
|
|
MOV AX,ROM_BIOS_DATA
|
||
|
|
MOV DS,AX
|
||
|
|
MOV BX,OFFSET BUFFER ;Clear the keyboard buffer.
|
||
|
|
MOV HEAD,BX
|
||
|
|
MOV TAIL,BX
|
||
|
|
MOV AH,15 ;Ask for service 15 of INT 10H
|
||
|
|
INT 10H ;This tells us how display is set up
|
||
|
|
MOV STATUS_PORT,03BAH ;Assume this is a monochrome display
|
||
|
|
TEST AL,4 ;Is it?
|
||
|
|
JNZ EXIT ;Yes - jump out
|
||
|
|
MOV SCREEN_SEG_OFFSET,8000H ;No - set up for graphics display
|
||
|
|
MOV STATUS_PORT,03DAH
|
||
|
|
|
||
|
|
EXIT: MOV DX,OFFSET LOAD_KEEPER ;Set up everything but LOAD_PAD to
|
||
|
|
INT 27H ;stay and attach itself to DOS
|
||
|
|
LOAD_KEEPER ENDP
|
||
|
|
|
||
|
|
CODE_SEG ENDS
|
||
|
|
|
||
|
|
END FIRST ;END "FIRST" so 8088 will go to FIRST first.
|
||
|
|
|
||
|
|
|
||
|
|
|