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| === The 6502 processor === | | === The 6502 processor === |
− | The 6502 processor can be seen as the 8bit micro ARM chip. | + | The 6502 processor can be seen as the 8-bit micro ARM chip. |
− | It has only has 3 registers (Accumilator, IX and IY registers) and only a handful of instructions to work with. | + | It has only has 3 registers (Accumulator, X and Y registers) and a handful of instructions to work with. |
| + | |
| + | === Adressing modes === |
| + | To be added. |
| | | |
| === Zero page === | | === Zero page === |
| When using the 6502 for sizecoding, you'll mostly be working from zeropage | | When using the 6502 for sizecoding, you'll mostly be working from zeropage |
| | | |
− | == Atari 8bit family == | + | == 6502 Based Platforms == |
− | The Atari XE/XL systems consists of the 6502 with custom hardware for graphics and sound.
| + | *'''[[Atari 8Bit]]''' - Atari 8-Bit Family (Atari XL/XE, etc.) |
− | | + | *'''[[Apple II]]''' - Apple II(e) |
− | === Setting up ===
| + | *'''[[Commodore 64]]''' - Commodore 64 |
− | Setting up your development platform for the Atari 8bit systems is quite easy, first get the following tools:
| + | *'''[[BBC Micro]]''' - Acorn BBC Micro/Master/Electron. |
− | | + | *'''[[Atari Lynx]]''' - Atari Lynx Handheld |
− | * Assembler: MADS Assembler - This assembler has nice macros for creating Binaries and SNA snapshot files out of the box. You can download it at https://mads.atari8.info/
| |
− | * Emulator(s): I Found Altirra to work best for my usecase. Make sure to use the original Rev2 rom for best compatibility. | |
− | | |
− | ==== Special Memory Adresses ====
| |
− | * FRAMECOUNTER_HIGH = 19 | |
− | * FRAMECOUNTER_LOW = 20 | |
− | | |
− | === Video display ===
| |
− | Video display on the Atari 8bit systems use the TIA chip, it has the following video modes:
| |
− | | |
− | To be added soon.
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− | | |
− | ==== Getting something on screen ====
| |
− | To be added soon.
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− | | |
− | <syntaxhighlight lang="6502">
| |
− | SDMCTL = $022f
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− | HPOSP0 = $d000
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− | SIZEP0 = $d008
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− | GRAFP0 = $d00d
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− | COLPM0 = $d012
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− | | |
− | FRAMECOUNTER_HIGH = 19
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− | FRAMECOUNTER = 20
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− | WSYNC = $d40a
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− | VCOUNT = $d40b
| |
− | | |
− | sinewave = $0600 ; to $06ff
| |
− | | |
− | org $80
| |
| | | |
− | main
| + | == Generic 6502 sinus table generator == |
− | ; disable all graphics/colors
| + | <syntaxhighlight lang=""> |
− | ldx #0
| |
− | stx SDMCTL
| |
− | | |
− | ldy #$7f
| |
− | sty SIZEP0 ; size p0=127
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− |
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| ldx #0 | | ldx #0 |
| ldy #$3f | | ldy #$3f |
Line 73: |
Line 40: |
| sta value_hi+1 | | sta value_hi+1 |
| | | |
− | sta sinewave+$c0,x | + | sta sintab+$c0,x |
− | sta sinewave+$80,y | + | sta sintab+$80,y |
| eor #$7f | | eor #$7f |
− | sta sinewave+$40,x | + | sta sintab+$40,x |
− | sta sinewave+$00,y | + | sta sintab+$00,y |
| | | |
| lda delta_lo+1 | | lda delta_lo+1 |
Line 88: |
Line 55: |
| dey | | dey |
| bpl make_sine | | bpl make_sine |
− |
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− | updateloop:
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− | ; vblank
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− | lda VCOUNT
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− | bne updateloop
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− |
| |
− | ; clear graphics
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− | sta HPOSP0
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− | sta GRAFP0
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− |
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− | ldy #0
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− | lda #47
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− | sta COLPM0
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− | yloop:
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− | tya ; graphics shape = y
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− | sta WSYNC
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− | sta GRAFP0
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− |
| |
− | ; a = sin(frame+y)+48
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− | tya
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− | adc FRAMECOUNTER
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− | tax
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− | lda sinewave,x
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− | adc #48
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− | sta HPOSP0
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− |
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− | iny
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− | bne yloop
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− | jmp updateloop
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− |
| |
− | run main
| |
− | </syntaxhighlight>
| |
− |
| |
− | === Sound ===
| |
− | The Atari 8bit systems use the Pokey chip to generate sound.
| |
− | To be added soon.
| |
− |
| |
− | ==== Make some noise ====
| |
− | To be added soon.
| |
− |
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− |
| |
− |
| |
− | === Additional Resources ===
| |
− | Sizecoding resource for the Atari 8bit are sparse
| |
− | * Fready's github (link to be added)
| |
− |
| |
− | == Atari Lynx ==
| |
− | The Atari Lynx consists of the 6502 with custom hardware for graphics and sound.
| |
− |
| |
− | === Setting up ===
| |
− | Setting up your development platform for the Atari Lynx:
| |
− |
| |
− | * Assembler: -
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− | * Emulator(s): -
| |
− |
| |
− | === Video display ===
| |
− | To be added soon.
| |
− |
| |
− | ==== Getting something on screen ====
| |
− | To be added soon.
| |
− |
| |
− |
| |
− | === Sound ===
| |
− | To be added soon.
| |
− |
| |
− | ==== Make some noise ====
| |
− | To be added soon.
| |
− |
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− | === Additional Resources ===
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− | Sizecoding resource for the Atari Lynx are sparse
| |
− | * 42Bastian's website (link to be added)
| |
− |
| |
− | == Commodore 64 ==
| |
− | The Commodore systems consists of the 6502 with custom hardware for graphics and sound.
| |
− |
| |
− | === Setting up ===
| |
− | Setting up your development platform for the Commodore systems is quite easy, first get the following tools:
| |
− |
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− | * Assembler: To be added
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− | * Emulator(s): VICE is the way to go
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− |
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− | === Autoboot ===
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− | <syntaxhighlight lang="6502">
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− | *=$0326
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− | .word start
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− | .byte $ed,$f6
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− | start
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− | ; rest of code
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− | </syntaxhighlight>
| |
− | Will give you autoboot and more space directly. (though writing through to $0400 will load it onto the screen unless you move the pointers)
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− |
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− | === Video display ===
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− | Video display on the Commodore, it has the following video modes:
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− |
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− | To be added soon.
| |
− |
| |
− | ==== Getting something on screen ====
| |
− | To be added soon.
| |
− |
| |
− |
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− | === Sound ===
| |
− | The Commodore 64 uses the famous SID chip to generate sound.
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− | To be added soon.
| |
− |
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− | ==== Make some noise ====
| |
− | To be added soon.
| |
− |
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− | === Additional Resources ===
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− | * links to be added
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− |
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− |
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− | == Apple II ==
| |
− | The Apple II is an 8-bit home computer and one of the world's first highly successful mass-produced microcomputer products. It was designed primarily by Steve Wozniak.
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− |
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− | === Setting up ===
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− | * ACME 6502 cross-assembler(https://sourceforge.net/projects/acme-crossass/)
| |
− | * Apple Commander (http://applecommander.sourceforge.net) for batch compilation
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− | * AppleWin emulator (https://github.com/AppleWin/AppleWin/releases). Supports Mockingboard card(AY-8910+speech synthesier), HDD, Z80 card(for CP/M), mouse etc.
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− | * CiderPress(https://a2ciderpress.com)
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− |
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− | Compilation can be done as follows (master.dsk can be found with applewin)
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− | <syntaxhighlight>
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− | acme hl.asm
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− | java -jar AppleCommander-1.3.5.jar -d master.dsk hl
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− | java -jar AppleCommander-1.3.5.jar -p master.dsk hl B 24576 < hl.bin
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− | </syntaxhighlight>
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− |
| |
− | === Memory Map ===
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− | <syntaxhighlight lang="6502">
| |
− | 0-255 $0-$FF ZERO-PAGE SYSTEM STORAGE
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− | 256-511 $100-$1FF SYSTEM STACK
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− | 512-767 $200-$2FF KEYBOARD CHARACTER BUFFER
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− | 768-975 $300-$3CF OFTEN AVAILABLE AS FREE SPACE FOR USER PROGRAMS
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− | 976-1023 $3D0-3FF SYSTEM VECTORS
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− | 1024-2047 $400-$7FF TEXT AND LO-RES GRAPHICS PAGE 1 <--- !!!
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− | 2048-LOMEM $800-LOMEM PROGRAM STORAGE
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− | 2048-3071 $800-$BFF TEXT AND LO-RES GRAPHICS PAGE 2 OR FREE SPACE
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− | 3072-8191 $C00-$1FFF FREE SPACE UNLESS RAM APPLESOFT IS IN USE
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− | 8192-16383 $2000-$3FFF HI-RES PAGE 1 OR FREE SPACE <--- !!!
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− | 16384-24575 $4000-$5FFF HI-RES PAGE 2 OR FREE SPACE
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− | 24576-38999 $6000-$95FF FREE SPACE AND STRING STORAGE
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− | 38400-49151 $9600-$BFFF DOS
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− | 49152-53247 $C000-$CFFF I/O HARDWARE (RESERVED)
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− | 53248-57343 $D000-$DFFF APPLESOFT IN LANGUAGE CARD OR ROM
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− | 57344-63487 $E000-$F7FF APPLESOFT OR INTEGER BASIC IN LANGUAGE CARD OR ROM
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− | 63488-65535 $F800-$FFFF SYSTEM MONITOR
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− | </syntaxhighlight>
| |
− |
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− | === Display ===
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− |
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− | === Graphics Modes ===
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− | : Text Mode 40x24, for Apple IIe available 80x25 - use PR#3 for switch mode, or hardware switch
| |
− | : LowRes 40x48, 16 colors: https://en.wikipedia.org/wiki/Apple_II_graphics
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− | : Hires mode 280x192,6 colors: https://www.xtof.info/blog/?p=768
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− | https://mrob.com/pub/xapple2/colors.html
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− | https://archive.org/details/HiRes_Color_Graphics_on_the_Apple_II_Computer_by_Wozniak
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− |
| |
− | However for sizecoding, you almost never want to do direct-access to graphics for Apple II in size-coding because the Apple II graphics modes are horrible. The only fast way to do things is with large lookup tables. To do hires you need to divide by 7 which as you can imagine is a bit difficult to do compactly on 6502. Double-hires is even crazier on top of that. Deater did manage a color-bar style effect in double-hires in 128B but that was doing some crazy tricks with the firmware BASIC routines, definitely not direct-access.
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− |
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− | Lores and Hires can be mixed modes and full-graphics
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− | The screen structure is called memory holes(https://retrocomputing.stackexchange.com/questions/2534/what-are-the-screen-holes-in-apple-ii-graphics). The GBASCALC($F847) procedure is used to calculate the address of the horizontal line : IN:reg.A=Y, out : GBASL/GBASH($26/$27)=address. See also https://www.callapple.org/uncategorized/use-of-apple-ii-color-graphics-in-assembly-language/
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− |
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− | ==== Getting something on screen ====
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− | Here is an example of a XOR texture, created by g0blinish
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− | <syntaxhighlight lang="6502">
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− | *=$6000
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− | !to "HL.bin", plain ; set output file and format
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− | !cpu 6502 ; set processor type
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− |
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− | GBASL = $26
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− | GBASH = $27
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− | SETGR = $FB40 ; setup LoRes
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− | GBASCALC = $F847 ; calc Address
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− |
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− | CLRTEXT = $C050 ;display graphics
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− | SETTEXT = $C051 ;display text
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− |
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− | CLRMIXED = $C052 ;clear mixed mode- enable full graphics
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− | SETMIXED = $C053 ;enable graphics/text mixed mode
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− |
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− | PAGE1 = $C054 ;select text/graphics page1
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− | PAGE2 = $C055 ;select text/graphics page2
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− |
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− | CLRHIRES = $C056 ;select Lo-res
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− | SETHIRES = $C057 ;select Hi-res
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− |
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− | TMP= $FA
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− |
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− | JSR SETGR ;GR
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− | BIT CLRMIXED ; full screen
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− |
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− | LDA #0 ; A=0
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− | STA TMP ; POKE $FA,A
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− |
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− | YLP ;
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− | LDA TMP ; A=PEEK($FA)
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− | ; LSR ; A=A/2
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− | JSR GBASCALC
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− | LDY #0;Y=0
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− |
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− | XLP TYA ; A=Y
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− | EOR TMP ; A=A xor PEEK($FA)
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− | and #$0F ; A=A and 15
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− | TAX ; X=A
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− | LDA COLORS,X ;A=PEEK(COLORS+X)
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− | STA(GBASL),Y ; POKE PEEK($26)+256*PEEK($27)+Y,A
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− | INY ; Y=Y+1
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− | CPY #40 ; Y=40?
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− | BNE XLP
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− | INC TMP ; POKE $FA,PEEK($FA)+1
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− | LDA TMP ; A=PEEK($FA)
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− | CMP #24 ; A=24?
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− | BNE YLP
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− |
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− | M1 JMP M1 ; replace to RTS
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− |
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− | COLORS ;N*17, pixel format is AAAABBBB, AAAA - upper dot, BBBB - lower dot
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− | !byte $00,$11,$22,$33,$44,$55,$66,$77
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− | !byte $88,$99,$AA,$BB,$CC,$DD,$EE,$FF
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− | </syntaxhighlight>
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− |
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− | ==== Sound ====
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− | Here is an example for using the speaker, based onthe following basic program:
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− |
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− | <syntaxhighlight lang="basic">
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− | ; 50 POKE 768,V: POKE 769,P - 255 * INT (P / 256): POKE 800,1 + P / 256
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− | ; 60 CALL 770: RETURN
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− | ; 95 FOR K = 1 TO N: READ V(K),P(K): NEXT K
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− | ; 100 FOR K = 1 TO N:V = V(K):P = P(K)
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− | ; 110 GOSUB 50
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− | ;!byte 173,48,192,136,208,5,206,1,3,240,9,202,208,245,174,0,3,76,2,3,206,32,3,208,240,96
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− | </syntaxhighlight>
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− |
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− | <syntaxhighlight lang="6502">
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− | *=$6000
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− | !to "HL.bin", plain ; set output file and format
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− | !cpu 6502 ; set processor type
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− |
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− | ;start
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− | ; 95 FOR K = 1 TO N: READ V(K),P(K): NEXT K
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− | ; 100 FOR K = 1 TO N:V = V(K):P = P(K)
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− | ini:
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− | lda #70
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− | sta cnt+1
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− | lda #music&255
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− | sta gotbyte+1
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− | lda #music/256
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− | sta gotbyte+2
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− |
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− | lop:
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− | ;V
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− | jsr gotbyte
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− | sta L300
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− | jsr gotbyte
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− | ;P
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− | jsr gotbyte
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− | sta L301
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− | jsr gotbyte
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− | clc
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− | adc #1
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− | sta L320
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− | jsr beep
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− |
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− | dec cnt+1
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− | cnt lda #70
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− | bne lop
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− | ; 110 GOSUB 50
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− | ; 50 POKE 768,V: POKE 769,P - 255 * INT (P / 256): POKE 800,1 + P / 256
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− | ; 60 CALL 770: RETURN
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− | jmp ini
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− | gotbyte
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− | lda music
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− | inc gotbyte+1
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− | bne noinch
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− | inc gotbyte+2
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− | noinch
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− | rts
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− | ;!byte 173,48,192,136,208,5,206,1,3,240,9,202,208,245,174,0,3,76,2,3,206,32,3,208,240,96
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− | beep:
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− | ldy #1
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− | ldx #1
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− | loc_302:
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− | LDA $C030
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− |
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− | loc_305:
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− | DEY
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− | BNE loc_30D
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− | DEC L301
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− | loc_30B:
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− | BEQ loc_316
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− |
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− | loc_30D:
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− | DEX
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− | BNE loc_305
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− | LDX L300
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− | JMP loc_302
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− | loc_316:
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− | DEC L320
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− | BNE loc_30B
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− | RTS
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− | L301 !byte 0
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− | L300 !byte 0
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− | L320 !byte 0
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− | music
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− | !word 76,192,85,64,96,64,102,64,114,128,114,64,96,64,102,64,114,64,128,64
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− | !word 114,64,152,64,171,64,152,512,76,192,85,64,96,64,102,64,114,128,114,64
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− | !word 96,64,102,64,114,64,128,64,114,64,152,64,171,64,152,512,85,64,85,64
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− | !word 85,64,96,64,144,128,144,64,128,64,76,128,85,64,96,64,144,128,114,64
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− | !word 96,64,102,128,114,64,128,64,128,128,114,64,128,64,114,512,85,64,85,64
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− | !word 85,64,96,64,144,128,144,64,128,64,76,128,85,64,96,64,144,128,114,64
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− | !word 96,64,102,128,114,64,128,64,128,64,128,128,96,64,85,64,96,64,102,64,114,64,114,64
| |
| </syntaxhighlight> | | </syntaxhighlight> |
| | | |
− | === Additional Resources === | + | === General 6502 Resources === |
− | * Deater's page on Apple II sizecoding http://www.deater.net/weave/vmwprod/demos/sizecoding.html | + | * 6502.org http://www.6502.org/ |
− | * Article on double hi-res http://www.battlestations.zone/2017/04/apple-ii-double-hi-res-from-ground-up.html | + | * 6502 instruction reference http://www.6502.org/tutorials/6502opcodes.html |
− | * Applesoft Hi-Res Subroutines : http://hackzapple.org/scripts_php/index.php?menu=5&mod=ASM&sub=AAL&sub2=8112&PHPSESSID=f65fabfd0cdbf56b6bdc0ddac25117c6#a2 | + | * 6502 books http://retro.hansotten.nl/6502-sbc/ |
| + | * 6502 Assembler tutorial https://dwheeler.com/6502/oneelkruns/asm1step.html |
| + | * Easy 6502 code tester https://skilldrick.github.io/easy6502/ |
| + | * Synthetic instructions https://wiki.nesdev.com/w/index.php/Synthetic_instructions#8-bit_rotate |
Wanting to start sizecoding on a 6502 platform in this day and age can be tough.
The 6502 processor can be seen as the 8-bit micro ARM chip.
It has only has 3 registers (Accumulator, X and Y registers) and a handful of instructions to work with.
To be added.