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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.
| |
| − | | |
| − | ==== Getting something on screen ====
| |
| − | To be added soon.
| |
| − | | |
| − | <syntaxhighlight lang="6502">
| |
| − | SDMCTL = $022f
| |
| − | HPOSP0 = $d000
| |
| − | SIZEP0 = $d008
| |
| − | GRAFP0 = $d00d
| |
| − | COLPM0 = $d012
| |
| − | | |
| − | FRAMECOUNTER_HIGH = 19
| |
| − | FRAMECOUNTER = 20
| |
| − | WSYNC = $d40a
| |
| − | VCOUNT = $d40b
| |
| − | | |
| − | sinewave = $0600 ; to $06ff
| |
| | | | |
| − | org $80
| + | == Generic 6502 sinus table generator == |
| − | | + | <syntaxhighlight lang=""> |
| − | main
| |
| − | ; disable all graphics/colors
| |
| − | ldx #0
| |
| − | stx SDMCTL
| |
| − | | |
| − | ldy #$7f
| |
| − | sty SIZEP0 ; size p0=127
| |
| − |
| |
| | 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 |
| − |
| |
| − | updateloop:
| |
| − | ; vblank
| |
| − | lda VCOUNT
| |
| − | bne updateloop
| |
| − |
| |
| − | ; clear graphics
| |
| − | sta HPOSP0
| |
| − | sta GRAFP0
| |
| − |
| |
| − | ldy #0
| |
| − | lda #47
| |
| − | sta COLPM0
| |
| − | yloop:
| |
| − | tya ; graphics shape = y
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| − | sta WSYNC
| |
| − | sta GRAFP0
| |
| − |
| |
| − | ; a = sin(frame+y)+48
| |
| − | tya
| |
| − | adc FRAMECOUNTER
| |
| − | tax
| |
| − | lda sinewave,x
| |
| − | adc #48
| |
| − | sta HPOSP0
| |
| − |
| |
| − | iny
| |
| − | bne yloop
| |
| − | jmp updateloop
| |
| − |
| |
| − | 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.
| |
| − |
| |
| − |
| |
| − |
| |
| − | === 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: -
| |
| − | * 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.
| |
| − |
| |
| − | === Additional Resources ===
| |
| − | 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:
| |
| − |
| |
| − | * Assembler: To be added
| |
| − | * Emulator(s): VICE is the way to go
| |
| − |
| |
| − | === Autoboot ===
| |
| − | <syntaxhighlight lang="6502">
| |
| − | *=$0326
| |
| − | .word start
| |
| − | .byte $ed,$f6
| |
| − | start
| |
| − | ; rest of code
| |
| − | </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)
| |
| − |
| |
| − | === Video display ===
| |
| − | Video display on the Commodore, it has the following video modes:
| |
| − |
| |
| − | To be added soon.
| |
| − |
| |
| − | ==== Getting something on screen ====
| |
| − | To be added soon.
| |
| − |
| |
| − |
| |
| − | === Sound ===
| |
| − | The Commodore 64 uses the famous SID chip to generate sound.
| |
| − | To be added soon.
| |
| − |
| |
| − | ==== Make some noise ====
| |
| − | To be added soon.
| |
| − |
| |
| − | === Additional Resources ===
| |
| − | * links to be added
| |
| − |
| |
| − |
| |
| − | == 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.
| |
| − |
| |
| − |
| |
| − | === Setting up ===
| |
| − | ACME 6502 cross-assembler(https://sourceforge.net/projects/acme-crossass/)
| |
| − | Apple Commander(http://applecommander.sourceforge.net) for batch compilation
| |
| − | AppleWin emulator(https://github.com/AppleWin/AppleWin/releases) -supports Mockingboard card(AY-8910+speech synthesier), HDD, Z80 card(for CP/M), mouse etc.
| |
| − | CiderPress(https://a2ciderpress.com)
| |
| − |
| |
| − | compilation can be done as follows (master.dsk can be found with applewin)
| |
| − | acme hl.asm
| |
| − | java -jar AppleCommander-1.3.5.jar -d master.dsk hl
| |
| − | java -jar AppleCommander-1.3.5.jar -p master.dsk hl B 24576 < hl.bin
| |
| − |
| |
| − | === Memory Map ===
| |
| − | <syntaxhighlight lang="6502">
| |
| − | 0-255 $0-$FF ZERO-PAGE SYSTEM STORAGE
| |
| − | 256-511 $100-$1FF SYSTEM STACK
| |
| − | 512-767 $200-$2FF KEYBOARD CHARACTER BUFFER
| |
| − | 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
| |
| − | 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
| |
| − | 38400-49151 $9600-$BFFF DOS
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| − | 49152-53247 $C000-$CFFF I/O HARDWARE (RESERVED)
| |
| − | 53248-57343 $D000-$DFFF APPLESOFT IN LANGUAGE CARD OR ROM
| |
| − | 57344-63487 $E000-$F7FF APPLESOFT OR INTEGER BASIC IN LANGUAGE CARD OR ROM
| |
| − | 63488-65535 $F800-$FFFF SYSTEM MONITOR
| |
| | </syntaxhighlight> | | </syntaxhighlight> |
| | | | |
| − | === Display === | + | === General 6502 Resources === |
| − | | + | * 6502.org http://www.6502.org/ |
| − | === Graphics Modes ===
| + | * 6502 instruction reference http://www.6502.org/tutorials/6502opcodes.html |
| − | Text Mode 40x24, 80x25 - use PR#3 for switch mode
| + | * 6502 books http://retro.hansotten.nl/6502-sbc/ |
| − | LoRes(https://en.wikipedia.org/wiki/Apple_II_graphics) 40x48, 16 colors
| + | * 6502 Assembler tutorial https://dwheeler.com/6502/oneelkruns/asm1step.html |
| − | Hires modes:
| + | * Easy 6502 code tester https://skilldrick.github.io/easy6502/ |
| − | https://www.xtof.info/blog/?p=768
| + | * Synthetic instructions https://wiki.nesdev.com/w/index.php/Synthetic_instructions#8-bit_rotate |
| − | https://mrob.com/pub/xapple2/colors.html
| |
| − | https://archive.org/details/HiRes_Color_Graphics_on_the_Apple_II_Computer_by_Wozniak
| |
| − | | |
| − | 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.
| |
| − | | |
| − | Lores and Hires can be mixed modes and full-graphics
| |
| − | 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/
| |
| − | | |
| − | ==== Sound ====
| |
| − | To be added soon.
| |
| − | | |
| − | === Additional Resources ===
| |
| − | * Deater's page on Apple II sizecoding http://www.deater.net/weave/vmwprod/demos/sizecoding.html | |
| − | * Article on double hi-res http://www.battlestations.zone/2017/04/apple-ii-double-hi-res-from-ground-up.html | |
| − | * Applesoft Hi-Res Subroutines : http://hackzapple.org/scripts_php/index.php?menu=5&mod=ASM&sub=AAL&sub2=8112&PHPSESSID=f65fabfd0cdbf56b6bdc0ddac25117c6#a2 | |
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.
ldx #0
ldy #$3f
make_sine:
value_lo
lda #0
clc
delta_lo
adc #0
sta value_lo+1
value_hi
lda #0
delta_hi
adc #0
sta value_hi+1
sta sintab+$c0,x
sta sintab+$80,y
eor #$7f
sta sintab+$40,x
sta sintab+$00,y
lda delta_lo+1
adc #8
sta delta_lo+1
bcc nothing
inc delta_hi+1
nothing
inx
dey
bpl make_sine
