Category: Atari

Added a new example to the repo called dli7 that creates a display list interrupt that manipulates the standard basic DL to display different background colors per textline. There is also a new python script in the repo to generate a Basic program that pokes the ML binary into memory and excutes it using USR(STARTADDRESS).
In the .asm file we ORG the binary to $4000 and in Basic we can excute it then using USR(16384).

This is the DLI asm

    run     start
    org     $4000

WSYNC       = $d40a
VCOUNT      = $d40b
COLPF2      = $d018
DL          = $cc

start
    lda     $0230
    sta     DL
    lda     $0231
    sta     DL+1
    lda     #<dli
    sta     $0200
    lda     #>dli
    sta     $0201

    ldy     #3
    lda     (DL),y
    eor     #128
    sta     (DL),y
    ldy     #8
dlloop
    lda     (DL),y
    eor     #128
    sta     (DL),y
    iny
    cpy     #29
    bne     dlloop
    lda     #192
    sta     $d40e

main
    lda     #$ff
    sta     $02fc
loop
    ldx     $02fc
    cpx     #$ff
    bne     exit
    jmp     loop
exit
    rts

dli
    pha
    lda     VCOUNT
    sta     WSYNC
    sta     COLPF2
    pla
    rti

Now you can assemble your code:
mads -l -t dli7.asm

And convert the .obx binary to basic program
python obx2bas.py --filename dli7.obx --start-addr 16384 --strip-header 12

This will generate a basic file dli.bas from the .obx

10 REM DLI7.BAS
20 FOR X=16384 TO 16457
30 READ D
40 POKE X, D
50 NEXT X
60 Z = USR(16384)
70 DATA 173,48,2,133,204,173,49,2
80 DATA 133,205,169,62,141,0,2,169
90 DATA 64,141,1,2,160,3,177,204
100 DATA 73,128,145,204,160,8,177,204
110 DATA 73,128,145,204,200,192,29,208
120 DATA 245,169,192,141,14,212,169,255
130 DATA 141,252,2,174,252,2,224,255
140 DATA 208,3,76,51,64,96,72,173
150 DATA 11,212,141,10,212,141,24,208
160 DATA 104,64

Now you can run the basic program
atari800 -pal -xl -basic -xlxe_rom ${ATARI_PATH}/roms/ATARIXL.ROM -basic_rom ${ATARI_PATH}/roms/ATARIBAS.ROM dli7.bas

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I revisted my Atari code snippets that i collected over the last 2 years to learn Atari 800 XL assember. I created a Github repo to make it easy yo access them.

Hello World DLI

Weganoid Game

Usage

1. Install mads assembler into your path
2. Install atari800 emulator into your path
3. Create helper scripts into your path to start the emulator

#!/bin/sh
ATARI_PATH="~/Devel/arch/atari"
${ATARI_PATH}/bin/atari800 -pal -xe -xlxe_rom ${ATARI_PATH}/roms/ATARIXL.ROM -video-accel -win-width 800 -win-height 600 "$1"

4. Build and run an example

cd hello 
make all

Links

• mads – MADS multi-pass crossassembler
• atari800 – Atari800 portable and free Atari 8-bit emulator
• sample code – Atari 800 XL code samples

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