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Example working
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‎.vscode/settings.json

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{
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"files.associations": {
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"*.s": "asm.6502"
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"*.s": "asm.6502",
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"*.i": "asm.6502"
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},
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"[asm.6502]": {
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"editor.insertSpaces": false,

‎.vscode/tasks.json

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{
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"label": "Build .prg",
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"type": "shell",
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"command": "make",
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"command": "just build",
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"problemMatcher": [],
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"group": {
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"kind": "build",

‎LICENSE

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Copyright (c) 2024 Carsten Elton Sørensen
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Permission is hereby granted, free of charge, to any person obtaining a copy of
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this software and associated documentation files (the "Software"), to deal in
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the Software without restriction, including without limitation the rights to
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use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
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of the Software, and to permit persons to whom the Software is furnished to do
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so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.

‎Makefile

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# Source files
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ASM_SRCS = \
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display.s \
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main.s
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# Extra dependencies

‎README.md

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# Introduction
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This repository contains a demonstration of how to set up a project for the MEGA65 computer using the ASMotor toolchain.
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It is not intended as an example of optimal, or even good, coding practices. It does demonstrate a few of the 45GS02 instructions, however.

‎src/display.i

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INCLUDE ONCE
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GLOBAL waitSOF
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GLOBAL clearScreen
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GLOBAL initDisplay
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TEXT_SCREEN EQU $000800
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CHARS_PER_LINE EQU 41

‎src/display.s

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INCLUDE "mega65.i"
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INCLUDE "zeropage.i"
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INCLUDE "display.i"
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SCREEN_HEIGHT EQU 200
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TOP_BORDER_POS EQU 42
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BOTTOM_BORDER_POS EQU TOP_BORDER_POS+SCREEN_HEIGHT*2-1
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BORDER_WIDTH EQU 80
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; ---------------------------------------------------------------------------
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; -- Wait for start of field
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; ---------------------------------------------------------------------------
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SECTION "waitSOF",CODE
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waitSOF::
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; test MSB of raster Y position
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bit R_YSCL
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bpl waitSOF
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.loop
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bit R_YSCL
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bmi .loop
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rts
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; ---------------------------------------------------------------------------
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; -- Initialize the first line of text and colour RAM.
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; ---------------------------------------------------------------------------
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SECTION "clearScreen",CODE
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clearScreen::
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; colour RAM
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ldq #COLOUR_RAM
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stq zp.tl0
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lda #$01
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bsr .clear
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; text screen
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ldq #TEXT_SCREEN
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stq zp.tl0
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lda #32 ; space screen code
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.clear
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ldz #CHARS_PER_LINE-1
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.loop
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sta [zp.tl0],z
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dez
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bpl .loop
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rts
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; ---------------------------------------------------------------------------
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; -- Initialise display registers to NTSC
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; ---------------------------------------------------------------------------
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SECTION "initDisplay",CODE
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initDisplay::
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ldz #0
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stz R_BORDERCOL
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stz R_SCREENCOL
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; 40 column
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stz R_VMODE
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lda #CHARS_PER_LINE
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sta R_CHRCOUNT
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stz R_LINESTEPL
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; set border position
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lda #<TOP_BORDER_POS
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sta R_TBDRPOSL
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stz R_TBDRPOSH
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lda #<BOTTOM_BORDER_POS
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sta R_BBDRPOSL
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lda #>BOTTOM_BORDER_POS
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sta R_BBDRPOSH
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; charset
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; ROM charset at $001000
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stz R_CHARPTRLSB
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lda #$10
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sta R_CHARPTRMSB
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stz R_CHARPTRBNK
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; text screen at TEXT_SCREEN
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lda #<TEXT_SCREEN
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sta R_SCRNPTRLSB
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lda #>TEXT_SCREEN
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sta R_SCRNPTRMSB
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lda #^TEXT_SCREEN
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sta R_SCRNPTRBNK
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; set text position
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lda #<BORDER_WIDTH
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sta R_TEXTXPOSL
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lda #>BORDER_WIDTH
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sta R_TEXTXPOSH
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; set borders
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lda #<TOP_BORDER_POS
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sta R_TEXTYPOSL
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lda #>TOP_BORDER_POS
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sta R_TEXTYPOSH
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lda #<BORDER_WIDTH
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sta R_SDBDRWDL
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lda #>BORDER_WIDTH
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sta R_SDBDRWDH
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; Scaling
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lda #120
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sta R_CHRXSCL
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lda #1
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sta R_CHRYSCL
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; set NTSC mode
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lda #R_RASLINE0.PALNTSC
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sta R_RASLINE0
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; set display generation
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lda #R_FNRASTERH.UPSCALE
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sta R_FNRASTERH
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stz R_MISC
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rts

‎src/main.s

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INCLUDE "mega65.i"
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INCLUDE "zeropage.i"
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INCLUDE "display.i"
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VECTOR_IRQ_BRK EQU $FFFE
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VECTOR_RESET EQU $FFFC
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VECTOR_NMI EQU $FFFA
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; ---------------------------------------------------------------------------
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; -- Main entry point
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; ---------------------------------------------------------------------------
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SECTION "Main",CODE
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Entry::
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sei
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; Ensure we're in 40 MHz mode
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lda #$41
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sta $00
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jsr initMemoryMap
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lda #<scrollText
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sta zp.scrolltext
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lda #>scrollText
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sta zp.scrolltext+1
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bsr initMemoryMap
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bsr initDisplay
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bsr clearScreen
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.main_loop
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bsr waitSOF
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bsr scroller
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bra .main_loop
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; ---------------------------------------------------------------------------
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; -- Scroller
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; ---------------------------------------------------------------------------
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SECTION "scroller",CODE
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scroller:
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; increase pixel position
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lda R_TEXTXPOSL
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dea
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cmp #80-16
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bne .bit_ok
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; copy chars to the left
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ldq #TEXT_SCREEN
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bsr .copy
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ldq #COLOUR_RAM
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bsr .copy
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ldq #TEXT_SCREEN+40
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stq zp.tl0
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ldz #0
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.next_char
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lda (zp.scrolltext),z
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bne .got_char
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.flash
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inc $d021
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bra .flash
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lda #<scrollText
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sta zp.scrolltext
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lda #>scrollText
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sta zp.scrolltext+1
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bra .next_char
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.got_char
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and #~$40 ; "convert" ASCII to screen code
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sta [zp.tl0],z
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inw zp.scrolltext
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lda #80
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.bit_ok
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sta R_TEXTXPOSL
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rts
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; copy CHARS_PER_LINE-1 bytes from Q+1 to Q
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.copy
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stq zp.tl0
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stq zp.tl1
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inq zp.tl1
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ldz #0
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.copy_loop
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lda [zp.tl1],z
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sta [zp.tl0],z
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inz
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cpz #CHARS_PER_LINE-1
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bne .copy_loop
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rts
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; ---------------------------------------------------------------------------
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; -- Initialize memory map
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; ---------------------------------------------------------------------------
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SECTION "initMemoryMap",CODE
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initMemoryMap:
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; Clear C65 memory map
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lda #$00
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taz
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map
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; Bank I/O in via C64 mechanism
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lda #$35
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sta $01
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; Do MEGA65 / VIC-IV I/O knock
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lda #$47
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sta $d02f
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lda #$53
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sta $d02f
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; Set IRQ vectors
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ldx #<emptyIrq
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ldy #>emptyIrq
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ldx #<.emptyIrq
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ldy #>.emptyIrq
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stx VECTOR_IRQ_BRK
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sty VECTOR_IRQ_BRK+1
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stx VECTOR_NMI
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; End MAP sequence, thus allowing interrupts to occur again
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eom
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rts
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; Bank I/O in via C64 mechanism
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lda #$35
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sta $01
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; Do MEGA65 / VIC-IV I/O knock
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lda #$47
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sta R_KEY
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lda #$53
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sta R_KEY
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; don't map rom
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lda #$00
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sta R_ROMEN
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rts
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emptyIrq:
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.emptyIrq:
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rti
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; ---------------------------------------------------------------------------
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; -- Data
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; ---------------------------------------------------------------------------
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SECTION "Text",DATA
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scrollText:
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DB "THIS IS A DEMONSTRATION OF HOW TO SET UP A PROJECT USING THE ASMOTOR ASSEMBLER AND LINKER ... ",0
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