mirror of
https://github.com/RevCurtisP/C02.git
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159 lines
6.4 KiB
NASM
159 lines
6.4 KiB
NASM
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; c02 Program Initialization Code for VIC-20 with 3K Expansion
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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 $03 ;Escape/Stop Key (RUN/STOP)
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RTNKEY EQU $0D ;Return/Enter Key (RETURN)
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;Zero Page Locations
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usradd EQU $01 ;Address of USR Routine
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linnum EQU $14 ;Integer Line Number Value
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txttab EQU $2B ;Pointer to Start of BASIC Program Text
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vartab EQU $2D ;Pointer to Start of BASIC Variable Storage Area
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arytab EQU $2F ;Pointer to Start of BASIC Array Storage Area
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strend EQU $31 ;Pointer to Start of Free RAM
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fretop EQU $33 ;Pointer to Bottom of String Text Storage Area
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memsiz EQU $37 ;Pointer to Highest Address Used by BASIC
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inpptr EQU $43 ;Pointer to Source of GET, READ, or INPUT Information
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facexp EQU $61 ;Floating Point Accumulator #1: Exponent
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facho EQU $62 ;Floating Point Accumulator #1: Mantissa
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facsgn EQU $66 ;Floating Point Accumulator #1: Sign
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fac2 EQU $69 ;Floating Point Accumulator #2
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argexp EQU $69 ;Floating Point Accumulator #2: Exponent
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argho EQU $6E ;Floating Point Accumulator #2: Mantissa
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argsgn EQU $6F ;Floating Point Accumulator #2: Sign
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chrget EQU $73 ;Subroutine: Get Next BASIC Text Character
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chrgot EQU $79 ;Entry Point: Get Current BASIC Text Character
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txtptr EQU $7A ;Pointer to Current BASIC Text Character
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pointb EQU $7C ;Entry Point: Test Character in Accumulator
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exit EQU $8A ;RTS at end of CHRGET, CHRGOT, and POINTB Routines
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status EQU $90 ;Kernal I/O Status Word
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ldtnd EQU $98 ;Number of Open I/O Files, Index to End of File Tables
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dfltn EQU $99 ;Default Input Device (Set to 0 for Keyboard)
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dflto EQU $9A ;Default Output (CMD) Device (Set to 3 for Screen)
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time EQU $A0 ;Software Jiffy Clock
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tape1 EQU $B2 ;Pointer: Start of Tape Buffer
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fnlen EQU $B7 ;Length of Current Filename
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la EQU $B8 ;Current Logical File Number
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sa EQU $B9 ;Current Secondary Address
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fa EQU $BA ;Current Device Number
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fnadr EQU $BB ;Pointer: Current Filename
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lste EQU $C5 ;Matrix Coordinate of Last Key Pressed
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ndx EQU $C6 ;Number of Characters in Keyboard Buffer
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rvs EQU $C7 ;Flag: Print Reverse Characters
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sfdx EQU $CB ;Matrix Coordinate of Current Key Pressed
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pnt EQU $D1 ;Pointer to Address of Current Screen Line
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pntr EQU $D3 ;Cursor Column on Current Line
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lnmx EQU $D5 ;Maximum Length of Physical Screen Line
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tblx EQU $D6 ;Current Cursor Physical Line Number
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insrt EQU $D8 ;Insert Mode (Number of Inserts)
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ldtb1 EQU $D9 ;Screen Line Link Table
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pntc EQU $F3 ;Pointer to Address of Current Screen Color RAM Location
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usrzp1 EQU $FB ;Free Byte for User Programs
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usrzp2 EQU $FC ;Free Byte for User Programs
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usrzp3 EQU $FD ;Free Byte for User Programs
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usrzp4 EQU $FE ;Free Byte for User Programs
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;Basic and Kernal Working Storage
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buf EQU $0200 ;BASIC Line Editor Input Buffer
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lat EQU $0259 ;Kernal Table of Active Logical File Numbers
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fat EQU $0263 ;Kernal Table of Device Numbers for Each Logical File
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sat EQU $026D ;Kernal Table of Secondary Addressed for Each Logical File
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keyd EQU $0277 ;Keyboard Buffer (Queue)
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memstr EQU $0281 ;Pointer: Operating System Start of Memory
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memsiz EQU $0283 ;Pointer: Operating System End of Memory
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color EQU $0286 ;Current Foreground Color Text
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hibase EQU $0288 ;Top Page of Screen Memory
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xmax EQU $0289 ;Maximum Keyboard Buffer Size
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rptflg EQU $028A ;Flag: Which Key Will Repeat?
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kount EQU $028B ;Counter for Timing Delay Between Key Repeats
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shflag EQU $028D ;Flag: SHIFT/CTRL/Logo Keypress
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mode EQU $0291 ;Flag: Change Character Sets with SHIFT/Logo Keypress
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user0 EQU $0310 ;Free Byte for User Programs
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user1 EQU $0311 ;Free Byte for User Programs
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user2 EQU $0312 ;Free Byte for User Programs
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user3 EQU $0313 ;Free Byte for User Programs
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user4 EQU $0334 ;Free Byte for User Programs
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user5 EQU $0335 ;Free Byte for User Programs
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user6 EQU $0336 ;Free Byte for User Programs
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user7 EQU $0337 ;Free Byte for User Programs
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user8 EQU $0338 ;Free Byte for User Programs
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user9 EQU $0339 ;Free Byte for User Programs
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user10 EQU $033A ;Free Byte for User Programs
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user11 EQU $033B ;Free Byte for User Programs
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tbffr EQU $033C ;Cassette I/O Buffer
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user12 EQU $03FC ;Free Byte for User Programs
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user13 EQU $03FD ;Free Byte for User Programs
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user14 EQU $03FE ;Free Byte for User Programs
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user15 EQU $03FF ;Free Byte for User Programs
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;Video RAM and ROM
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vicscn EQU $1E00 ;Video Screen Memory Area (Unexpanded)
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chrrom EQU $8000 ;Character Generator ROM
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vicclr EQU $9600 ;Color RAM (Unexpanded)
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;Kernal Routines
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chrin EQU $FFCF ;Input Character to Channel
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chrout EQU $FFD2 ;Output Character to Channel
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getin EQU $FFE4 ;Read Character from Keyboard Buffer
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;Machine Language Basic Stub
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ORG $0401 ;Start
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basic: DC $0C, $04 ; Pointer to Next Line (1036)
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DC $00, $00 ; Line Number (0)
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DC $9E ; SYS
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DC $20 ; ' '
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DC $31, $30, $33 ,$38 ; "1038"
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DC $00 ;End of Line Marker
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DC $00, $00 ;End of Basic Program
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start: TSX ;Get Stack Pointer
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STX user15 ;and Save for Exit
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JMP main ;Execute Program
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exit: LDX user15 ;Retrieve Saved Stack Pointer
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TXS ;and Restore It
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RTS ;Return to BASIC
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;Poll Keyboard for Character
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plkey EQU getin ;Read Character from Keyboard Buffer
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;Get Character from Keyboard
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getkey:
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;Wait for Character from Keyboard
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rdkey: JSR plkey ;Poll Keyboard
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BEQ getkey ;If No Key, Loop
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RTS
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;Delete Previous Character
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delchr: RTS
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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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;Print Character to Console
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prchr EQU chrout ;
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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 Nybble
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CMP #$0A ;If Low Nybble >= 10
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BCC prhexc ;
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ADC #$06 ; Convert ':' to 'A'...
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prhexc: ADC #$30 ;Convert to ASCII Character
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JMP prchr ;Print Hex Digit and Return
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exit: RTS ;Return to Monitor
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