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https://github.com/RevCurtisP/C02.git
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114 lines
3.5 KiB
Plaintext
114 lines
3.5 KiB
Plaintext
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; C02 Program Initialization Code for BBC Micro
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;System Specific ASCII Key Mappings
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DELKEY EQU $7F ;Delete/Backspace Key ($08=Backspace, $7F=Delete)
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ESCKEY EQU $1B ;Escape/Stop Key ($03=Ctrl-C, $1B=Escape)
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RTNKEY EQU $0D ;Return/Enter Key ($0D=Carriage Return)
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NULKEY EQU $00 ;No Key was Pressed ($00=Null)
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;Zero Page Locations
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SRCPTR EQU $70 ;Source Pointer
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DSTPTR EQU $72 ;Destination String Pointer (string.asm)
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BFRLO EQU $74 ;Buffer Pointer LSB [Temporary String Pointer]
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BFRHI EQU $75 ;Buffer Pointer MSB [Temporary String Pointer]
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BLKPTR EQU $76 ;Block Pointer
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STKLO EQU $78 ;Stack Pointer
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STKHI EQU $79 ; Unused by OS
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TEMP0 EQU $80 ;Temporary Storage
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TEMP1 EQU $81
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TEMP2 EQU $82
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TEMP3 EQU $83
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BLKBGN EQU $84 ;Block Start Address
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BLKEND EQU $86 ;Block End Address
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STKSLO EQU $88 ;Stack Start Address
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STKSHI EQU $89
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STKELO EQU $8A ;Stack End Address
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STKEHI EQU $8B
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; EQU $8C ;Unused
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; EQU $8D ;Unused
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; EQU $8E ;Unused
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RANDOM EQU $8F ;Pseudo-RANDOM Number Storage
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RDSEED EQU $0296 ;System Clock Low Byte
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ORG $1900 ;Program Start Address
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START: JMP MAIN ;Execute Program
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;Exit Program and Return to Operating System or Monitor
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EXIT: JMP ($FFFC) ;Execute Warm Start
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;Poll Character from Keyboard
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PLKEY: LDA #$81 ;Set Command to Read Key
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LDY #0 ;Set Time Limit to 0
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LDX #0
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JSR #FFF4 ;Call OSBYTE
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TYA ;Check Status Code
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BNE GETCHE ;If Error, Check for Escape
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TXA ;Else Return Character
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RTS
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;Read Character from Console
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GETKEY; ;Usually Drops into RDKEY, but may need to call RDKEY
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; then clean/convert returned value (e.g. Apple-1)
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;Wait for Character from Keyboard
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GETCHR: JSR $FFE0 ;Call System Routine OSRDCH
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BCC GETCHX ;If Error
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GETCHE: CMP #$1B ;
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BNE GETCHZ ; If Escape Pressed
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LDA #$7E ; Acknowledge It
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JSR $FFF4 ; with OSBYTE Call
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LDA #$1B ; and Return ESC
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BNE GETCHX ; Else
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GETCHZ: LDA #0 ; Return 0
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GETCHX: RTS
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;Delete Previous Character
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DELCHR: LDA #$7F ;Print DEL Character
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JMP PUTCHR
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;Advance Cursor to Next line
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NEWLIN EQU $FFE7 ;Aliased to System Routine OSNEWL
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;Print Character to Screen
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PUTCHR: EQU $FFE3 ;Aliased to OSASCI System Routine
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;Clear the Screen
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CLRSCR: LDA #$0C ;Print FF Character
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JMP PUTCHR
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;Move Cursor to Specified Coordinates
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SETPOS: TAX ;Save Column in X
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LDA #$1F ;Issue Move Cursor Command
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JSR PUTCHR
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TXA ;Send X Coordinate
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JSR PUTCHR
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TYA ;Send Y Coordinate
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JMP PUTCHR
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;Get Cursor Position
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GETPOS: LDA $0318 ;Load Text Cursor X Coordinate
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LDY #0319 ;Load Text Cursor Y Coordinate
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RTS
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;Get Screen Size
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GETSIZ: LDA $030A ;Get Right Side of Text Window
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SEC
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SBC $0308 ;Subtract Left Side of Text Window
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TAX ;Copy to X Register
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INX ;and Add 1
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LDA $0309 ;Get Bottom of Text Window
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SEC
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SBC $030B ;Subtract Top of Text Window
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TAY ;Copy to Y Register
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INY ;and Add 1
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TXA ;Copy Width to Accumulator
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RTS ;Return Screen Width in A, Height in Y
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INCLUDE "../include/prbyte.a02" ;PRBYTE and PRHEX routine
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INCLUDE "../include/putstr.a02" ;PUTSTR routine
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