mirror of
https://github.com/sehugg/8bitworkshop.git
synced 2024-12-01 13:50:30 +00:00
166 lines
6.2 KiB
NASM
166 lines
6.2 KiB
NASM
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ORG 04000H
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; LOAD 04000H
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; MSX cartridge header @ 0x4000 - 0x400f
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dw 0x4241
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dw Start
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dw Start
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dw 0,0,0,0,0
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; ******************************
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; * BIOS STANDARD ROUTINES *
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; ******************************
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RDSLT: EQU 000CH
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CNVCHR: EQU 00ABH
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MAPXYC: EQU 0111H
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SETC: EQU 0120H
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; ******************************
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; * WORKSPACE VARIABLES *
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; ******************************
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FORCLR: EQU 0F3E9H
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ATRBYT: EQU 0F3F2H
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CGPNT: EQU 0F91FH
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PATWRK: EQU 0FC40H
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SCRMOD: EQU 0FCAFH
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GRPACX: EQU 0FCB7H
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GRPACY: EQU 0FCB9H
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; ******************************
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; * CONTROL CHARACTERS *
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; ******************************
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CR: EQU 13
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Start:
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GFORTY: CP 3 ; String type?
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RET NZ ;
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LD A,(SCRMOD) ; Mode
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CP 2 ; Graphics?
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RET NZ ;
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EX DE,HL ; HL->Descriptor
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LD B,(HL) ; B=String len
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INC HL ;
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LD E,(HL) ; Address LSB
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INC HL ;
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LD D,(HL) ; DE->String
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INC B ;
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GF2: DEC B ; Finished?
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RET Z ;
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LD A,(DE) ; A=Chr from string
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CALL GPRINT ; Print it
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INC DE ;
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JR GF2 ; Next chr
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GPRINT: PUSH AF ;
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PUSH BC ;
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PUSH DE ;
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PUSH HL ;
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PUSH IY ;
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LD BC,(GRPACX) ; BC=X coord
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LD DE,(GRPACY) ; DE=Y coord
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CALL GDC ; Decode chr
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LD (GRPACX),BC ; New X coord
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LD (GRPACY),DE ; New Y coord
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POP IY ;
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POP HL ;
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POP DE ;
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POP BC ;
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POP AF ;
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RET ;
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GDC: CALL CNVCHR ; Check graphic
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RET NC ; NC=Header
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JR NZ,GD2 ; NZ=Converted
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CP CR ; Carriage Return?
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JR Z,GCRLF ;
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CP 20H ; Other control?
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RET C ; Ignore
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GD2: LD L,A ;
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LD H,0 ; HL=Chr code
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ADD HL,HL ;
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ADD HL,HL ;
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ADD HL,HL ; HL=Chr*8
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PUSH BC ; X coord
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PUSH DE ; Y coord
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LD DE,(CGPNT+1) ; Character set
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ADD HL,DE ; HL->Pattern
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LD DE,PATWRK ; DE->Buffer
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LD B,8 ; Eight byte pattern
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GD3: PUSH BC ;
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PUSH DE ;
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LD A,(CGPNT) ; Slot ID
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CALL RDSLT ; Get pattern
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EI ;
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POP DE ;
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POP BC ;
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LD (DE),A ; Put in buffer
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INC DE ;
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INC HL ;
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DJNZ GD3 ; Next
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POP DE ;
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POP BC ;
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LD A,(FORCLR) ; Current colour
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LD (ATRBYT),A ; Set ink
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LD IY,PATWRK ; IY->Patterns
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PUSH DE ;
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LD H,8 ; Max dot rows
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GD4: BIT 7,D ; Pos Y coord?
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JR NZ,GD8 ;
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CALL BMDROW ; Bottom most row?
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JR C,GD9 ; C=Y too large
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PUSH BC ;
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LD L,6 ; Max dot cols
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LD A,(IY+0) ; A=Pattern row
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GD5: BIT 7,B ; Pos X coord
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JR NZ,GD6 ;
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CALL RMDCOL ; Rightmost col?
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JR C,GD7 ; C=X too large
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BIT 7,A ; Pattern bit
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JR Z,GD6 ; Z=0 Pixel
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PUSH AF ;
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PUSH DE ;
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PUSH HL ;
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CALL MAPXYC ; Map coords
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CALL SETC ; Set pixel
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POP HL ;
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POP DE ;
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POP AF ;
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GD6: RLCA ; Shift pattern
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INC BC ; X=X+1
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DEC L ; Finished dot cols?
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JR NZ,GD5 ;
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GD7: POP BC ; Initial X coord
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GD8: INC IY ; Next pattern byte
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INC DE ; Y=Y+1
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DEC H ; Finished dot rows?
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JR NZ,GD4 ;
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GD9: POP DE ; Initial Y coord
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LD HL,6 ; Step
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ADD HL,BC ; X=X+6
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LD B,H ;
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LD C,L ; BC=New X coord
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CALL RMDCOL ; Rightmost col?
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RET NC ;
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GCRLF: LD BC,0 ; X=0
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LD HL,8 ;
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ADD HL,DE ;
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EX DE,HL ; Y=Y+8
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RET ;
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BMDROW: PUSH HL ;
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LD HL,191 ; Bottom dot row
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OR A ;
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SBC HL,DE ; Check Y coord
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POP HL ;
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RET ; C=Below screen
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RMDCOL: PUSH HL ;
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LD HL,239 ; Rightmost dot col
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OR A ;
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SBC HL,BC ; Check X coord
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POP HL ;
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RET ; C=Beyond right
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END
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