mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2025-08-15 20:27:21 +00:00
65 lines
2.5 KiB
NASM
65 lines
2.5 KiB
NASM
*``````````````````````````````*
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* LRGFCLR (NATHAN RIGGS) *
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* *
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* FILLS THE LORES SCREEN WITH *
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* THE SPECIFIED COLOR. *
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* *
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* INPUT: *
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* *
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* .A = BACKGROUND COLOR *
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* *
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* NONE *
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* *
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* DESTROY: NZCIDV *
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* ^^^ ^ *
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* *
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* CYCLES: 125+ *
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* SIZE: 86 BYTES *
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*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
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*
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]C EQU ZPB1 ; TEMPORARY COLOR STORAGE
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*
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LRGFCLR
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STA ]C ; {4C3B} STORE COLOR
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ASL ; {2C1B} SHIFT LOW BYTE OF COLOR
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ASL ; {2C1B} INTO THE HIGH BYTE, SINCE
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ASL ; {2C1B} THE HIGH BYTE IS ALWAYS 0
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ASL ; {2C1B}
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CLC ; {2C1B} CLEAR CARRY
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ADC ]C ; {4C3B} ADD LOW BYTE TO NEW HIGH
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STA ]C ; {4C3B} SO IT'S A REPEATING NIBBLE
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LDY #$78 ; {3C2B} BYTE LENGTH FOR EACH LINE
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; THIS ALLOWS FOR FILLING EVERY PIXEL
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LDX LWP ; {4C3B} CHECK WHICH PAGE TO CLEAR
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CPX #2 ; {3C2B} IS IT PAGE 2?
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BEQ :P2 ; {3C2B} IF SO, CLEAR PAGE 2
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; OTHERWISE, ASSUME PAGE 1
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:LP1
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STA $400,Y ; {4C3B} PLOT FIRST SECTION
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STA $480,Y ; {4C3B} PLOT SECOND
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STA $500,Y ; {4C3B} THIRD
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STA $580,Y ; {4C3B} FOURTH
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STA $600,Y ; {4C3B} FIFTH
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STA $680,Y ; {4C3B} SIXTH
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STA $700,Y ; {4C3B} SEVENTH
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STA $780,Y ; {4C3B} EIGHTH
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DEY ; {2C1B} DECREASE OFFSET COUNTER
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BPL :LP1 ; {3C2B} IF NOT NEGATIVE, KEEP LOOPING
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JMP :EXIT ; {3C3B}
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:P2
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LDA ]C ; {4C3B}
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LDY #$78 ; {3C2B}
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:LP2
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STA $800,Y ; {4C3B} PLOT FIRST SECTION
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STA $880,Y ; {4C3B} PLOT SECOND
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STA $900,Y ; {4C3B} THIRD
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STA $980,Y ; {4C3B} FOURTH
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STA $0A00,Y ; {4C3B} FIFTH
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STA $0A80,Y ; {4C3B} SIXTH
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STA $0B00,Y ; {4C3B} SEVENTH
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STA $0B80,Y ; {4C3B} EIGHTH
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DEY ; {2C1B} DECREASE OFFSET COUNTER
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BPL :LP2 ; {3C2B} IF NOT NEGATIVE, KEEP LOOPING
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:EXIT
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RTS ; {6C1B}
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