mirror of
https://github.com/RevCurtisP/C02.git
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81 lines
2.4 KiB
NASM
81 lines
2.4 KiB
NASM
; py65mon program initialization code for c02 programs
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;System Specific ASCII Key Mappings
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DELKEY EQU $7F ;Delete/Backspace Key (Delete)
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ESCKEY EQU $1B ;Escape/Stop Key (Escape)
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RTNKEY EQU $0D ;Return/Enter Key (Carriage Return)
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;Zero Page Locations
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strlo EQU $30 ;String Pointer (stdio.asm)
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strhi EQU $31
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dstlo EQU $32 ;Source String Pointer (string.asm)
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dsthi EQU $33
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rdseed EQU $3E ;Pseudo-Random Seed
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random EQU $3F ;Pseudo-Random Number Storage
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temp0 EQU $40 ;Temporary Storage
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temp1 EQU $41
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temp2 EQU $42
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;Memory Mapped I/O
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putc EQU $F001 ;Write Character to Console
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getc EQU $F004 ;Read Character from Console
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ORG $0200 ;Start Directly Above Stack
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start: JMP main ;Execute Program
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;Poll Character from Keyboard
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plkey: INC rdseed ;Cycle the Random Seed (if not provided by system)
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LDA getc ;Read Character from Console
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RTS
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;Read Character from Console
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getkey; ;Same As rdkey
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;Wait for Character from Console
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rdkey: JSR plkey ;Read Character from Console
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BEQ rdkey ; Loop if None Received
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RTS
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;Delete Previous Character
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delchr: LDA #$08 ;Load Backspace into Accumulator
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JSR prchr ; and Print it
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LDA #$20 ;Load Space into Accumulater
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JSR prchr ; and Print it
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LDA #$08 ;Load Backspace into Accumulator
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JMP prchr ; and Print it
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;Advance Character to Next line
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newlin: LDA #$0D ;Load C/R into Accumulator
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JSR prchr ; and Print it
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LDA #$0A ;Load L/F into Accumulater
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; and fall into prchr
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;Print Character to Console
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prchr: STA putc ;Write Character to Console
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RTS
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exit: BRK ;Return to Monitor
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;Print Byte as Two-Digit Hex Number to Console
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prbyte: PHA ;Save Accumulater
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LSR ;Shift Hi Nybble to Low Nybble
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LSR
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LSR
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LSR
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JSR prhex ; and Print it
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PLA ;Restore Accumulator
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; and fall into prhex
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;Print Low Nybble as Hex Digit to Console
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prhex: AND #$0F ;Strip High Nybb
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SED ;Set Decimal Flag for
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CLC ; Addition Wizardry
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ADC #$90 ;Convert to $90-$99,$00-$05
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ADC #$40 ;Convert to $30-$39,$41-$46
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CLD ;Clear Decimal Flag
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JMP prchr ;Print Hex Digit and Return
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