137 lines
4.3 KiB
NASM
137 lines
4.3 KiB
NASM
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CGROUP GROUP VECTOR,CODESEG
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VECTOR SEGMENT AT 0H
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DB 6CH DUP(?) ;FILLER
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TIME_LO DW ? ;DOS TIME
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TIME_HI DW ? ;DOS TIME
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VEC_IP DW ;CLOCK UPDATE VECTOR IP
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VEC_CS DW ;CLOCK UPDATE VECTOR CS
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VECTOR ENDS
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CODESEG SEGMENT PARA
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ASSUME CS:CODESEG,DS:CGROUP
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ORG 100H
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CLK PROC FAR
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JMP SETUP ;ATTACH TO DOS
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INTRPT LABEL DWORD
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INT_IP DW 0 ;OLD UPDATE VECTOR IP
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INT_CS DW 0 ;OLD UPDATE VECROR CS
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TICKS DW 0 ;TICK COUNTER
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SCR_OFF DB 0,0 ;SCREEN OFFSET IN BUFFER
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CRT_PORT DW 0 ;SCREEN STATUS PORT
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flag db 0
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TIME DB 8 DUP(':',0BH) ;TIME SAVE AREA
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CLK_INT LABEL NEAR
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PUSH AX ;SAVE REGISTERS
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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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PUSHF ; AND FLAGS
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CALL CS:[INTRPT] ;DO OLD UPDATE INTERRUPT
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MOV CX,0040H ;GET SEGMENT OF DOS TABLE
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MOV DS,CX ;PUT IN DS
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MOV CX,CS:TICKS ;GET TICK COUNT
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INC CX ;INCREMENT IT
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CMP CX,20 ;01F4H ;HAS A MINUTE GONE BY?
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JB NO_MINUTE ;NO, MOVE ON
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CALL UPDATE ;YES, UPDATE CLOCK AND
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MOV CX,0 ; RESET TICK COUNTER
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NO_MINUTE:
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MOV CS:TICKS,CX ;SAVE UPDATED TICK COUNT
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MOV CX,0B000H ;GET VIDEO SEGMENT
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MOV ES,CX ;PUT IN ES
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MOV DX,CS:CRT_PORT ;GET CRT STATUS PORT ADDR
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MOV DI,WORD PTR CS:SCR_OFF ;GET SCREEN BUFFER OFFSET
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LEA SI,CS:TIME ;GET DOS TIME
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MOV CX,16 ;SET UP TO MOVE 10 BYTES
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CLI ;DISABLE OTHER INTERRUPTS
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WAIT1: IN AL,DX ;READ CRT STATUS
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TEST AL,1 ;CHECK FOR VERTICAL RETRACE
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JNZ WAIT1 ;WAIT FOR RETRACE LOW
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MOV AH,CS:[SI] ;GET FIRST BYTE TO MOVE
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WAIT2: IN AL,DX ;GET CRT STATUS
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TEST AL,1 ;CHECK FOR VERTICAL RETRACE
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JZ WAIT2 ;WAIT FOR RETRACE HIGH
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MOV ES:[DI],AH ;MOVE BYTE TO SCREEN
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INC DI ;INCREMENT INDEX
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INC SI
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LOOP WAIT1 ;MOVE NEXT BYTE
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STI ;ENABLE INTERRUPTS
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POP ES ;RESTORE REGISTERS
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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 AX
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IRET ;RETURN FROM INTERRUPT
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CLK ENDP
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UPDATE PROC NEAR
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PUSH AX ;SAVE REGISTERS
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PUSH BX
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PUSH CX
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PUSH DX
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PUSH DS
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MOV AX,0040H ;GET ADDRESS OF DOS TABLE
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MOV DS,AX ;PUT IN DS
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MOV AX,TIME_HI ;GET HIGH BYTE OF DOS TIME
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mov flag,0 ;am flag
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HOUR: CMP AX,0CH ;CONVERT TO HOURS
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JLE H1
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mov flag,1 ;set to pm
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SUB AX,0CH
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JMP HOUR
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H1: AAM ;CONVERT TO ASCII
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ADD AX,3030H
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LEA BX,CS:TIME ;GET ADDRESS OF TIME AREA
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MOV CS:[BX],AH ;SAVE HOURS FIRST DIGIT
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MOV CS:[BX+2],AL ;SAVE HOURS SECOND DIGIT
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MOV AX,TIME_LO ;GET DOS TIME LOW BYTE
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MOV CX,8H ;CONVERT TO MINUTES
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SHR AX,CL
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MOV DX,3CH
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MUL DL
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SHR AX,CL
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AAM ;CONVERT TO ASCII
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ADD AX,3030H
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MOV CS:[BX+6],AH ;SAVE MINUTES FIRST DIGIT
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MOV CS:[BX+8],AL ;SAVE MINUTES SECOND DIGIT
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mov byte ptr cs:[bx+12],'a'
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cmp flag,0 ;is it am?
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jz goahead
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mov byte ptr cs:[bx+12],'p'
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goahead:
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mov byte ptr cs:[bx+14],'m'
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POP DS ;RESTORE REGISTERS
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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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RET
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UPDATE ENDP
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SETUP: MOV AX,0 ;GET ADDRESS OF VECTOR TABLE
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MOV DS,AX ;PUT IN DS
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CLI ;DISABLE FURTHER INTERRUPTS
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MOV AX,[VEC_IP] ;GET ADDRESS OF OLD UPDATE IP
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MOV CS:[INT_IP],AX ;SAVE IT
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MOV AX,[VEC_CS] ;GET ADDRESS OF OLD UPDATE CS
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MOV CS:[INT_CS],AX ;SAVE IT
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MOV VEC_IP,OFFSET CLK_INT ;PUT ADDRESS OF CLK IN VECTOR IP
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MOV VEC_CS,CS ;PUT CS OF CLK IN VECTOR CS
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STI ;ENABLE INTERRUPTS
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MOV AH,0FH ;READ VIDEO STATUS
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INT 10H
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SUB AH,8 ;SUBTRACT 8 CHAR TIME FROM NCOLS
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SHL AH,1 ;MULTIPLY BY 2 FOR ATTRIBUTE
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MOV CS:SCR_OFF,AH ;SAVE SCREEN TIME LOCATION
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MOV WORD PTR CS:CRT_PORT,03BAH ;SAVE MONO STATUS PORT ADDR
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TEST AL,4 ;CHECK FOR COLOR MONITOR
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JNZ MONO ;IF MONO, MOVE ON
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ADD WORD PTR CS:SCR_OFF,8000H ;ADD COLOR OFFSET TO TIME OFFSET
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MOV WORD PTR CS:CRT_PORT,03DAH ;SAVE COLOR STATUS PORT ADDR
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MONO: CALL UPDATE ;DO FIRST UPDATE & PRINT TIME
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MOV DX,OFFSET SETUP ;GET END ADDRESS OF NEW INTERRUPT
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INT 27H ;TERMINATE AND REMAIN RESIDENT
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DB 117 DUP(0) ;FILLER
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CODESEG ENDS
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END CLK
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