Difference between revisions of "6502"

From SizeCoding
Jump to: navigation, search
 
(55 intermediate revisions by 9 users not shown)
Line 7: Line 7:
  
 
=== 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
 
  
−
main
+
== Generic 6502 sinus table generator ==
−
; disable all graphics/colors
+
<syntaxhighlight lang="">
−
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
 
−
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)
 
−
<syntaxhighlight>
 
−
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
 
−
</syntaxhighlight>
 
−
 
−
=== 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
 
−
  976-1023    $3D0-3FF    SYSTEM VECTORS
 
−
1024-2047    $400-$7FF    TEXT AND LO-RES GRAPHICS PAGE 1 <--- !!!
 
−
2048-LOMEM    $800-LOMEM  PROGRAM STORAGE
 
−
2048-3071    $800-$BFF    TEXT AND LO-RES GRAPHICS PAGE 2 OR FREE SPACE
 
−
3072-8191    $C00-$1FFF  FREE SPACE UNLESS RAM APPLESOFT IS IN USE
 
−
8192-16383  $2000-$3FFF  HI-RES PAGE 1 OR FREE SPACE <--- !!!
 
−
16384-24575  $4000-$5FFF  HI-RES PAGE 2 OR FREE SPACE
 
−
24576-38999  $6000-$95FF  FREE SPACE AND STRING STORAGE
 
−
38400-49151  $9600-$BFFF  DOS
 
−
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>
 
−
 
−
=== Display ===
 
−
 
−
=== Graphics Modes ===
 
−
Text Mode 40x24, 80x25 - use PR#3 for switch mode
 
−
LowRes: https://en.wikipedia.org/wiki/Apple_II_graphics
 
−
 
−
40x48, 16 colors Hires modes: https://www.xtof.info/blog/?p=768
 
−
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/
 
−
 
−
==== Getting something on screen ====
 
−
Here is an example of a XOR texture, created by g0blinish
 
−
<syntaxhighlight lang="6502">
 
−
*=$6000
 
−
!to "HL.bin", plain ; set output file and format
 
−
!cpu 6502 ; set processor type
 
−
 
−
GBASL = $26
 
−
GBASH = $27
 
−
SETGR    =    $FB40 ; setup LoRes
 
−
GBASCALC = $F847 ; calc Address
 
−
 
−
CLRTEXT =  $C050 ;display graphics
 
−
SETTEXT =  $C051 ;display text
 
−
 
−
CLRMIXED = $C052 ;clear mixed mode- enable full graphics
 
−
SETMIXED = $C053 ;enable graphics/text mixed mode
 
−
 
−
PAGE1 =    $C054 ;select text/graphics page1
 
−
PAGE2 =    $C055 ;select text/graphics page2
 
−
 
−
CLRHIRES = $C056 ;select Lo-res
 
−
SETHIRES = $C057 ;select Hi-res
 
−
 
−
TMP= $FA
 
−
 
−
JSR  SETGR      ;GR
 
−
BIT CLRMIXED ; full screen
 
−
 
−
LDA #0 ; A=0
 
−
STA TMP ; POKE $FA,A
 
−
 
−
YLP ;
 
−
LDA TMP ; A=PEEK($FA)
 
−
; LSR ; A=A/2
 
−
JSR GBASCALC
 
−
LDY #0;Y=0
 
−
 
−
XLP TYA ; A=Y
 
−
EOR TMP ; A=A xor PEEK($FA)
 
−
and #$0F ; A=A and 15
 
−
TAX ; X=A
 
−
LDA COLORS,X ;A=PEEK(COLORS+X)
 
−
STA(GBASL),Y ; POKE PEEK($26)+256*PEEK($27)+Y,A
 
−
INY ; Y=Y+1
 
−
CPY #40 ; Y=40?
 
−
BNE XLP
 
−
INC TMP ; POKE $FA,PEEK($FA)+1
 
−
LDA TMP ; A=PEEK($FA)
 
−
CMP #24 ; A=24?
 
−
BNE YLP
 
−
 
−
M1 JMP M1 ; replace to RTS
 
−
 
−
COLORS ;N*17, pixel format is AAAABBBB, AAAA(lower nibble) - upper dot, BBBB - lower dot
 
−
!byte $00,$11,$22,$33,$44,$55,$66,$77
 
−
!byte $88,$99,$AA,$BB,$CC,$DD,$EE,$FF
 
−
</syntaxhighlight>
 
−
 
−
==== Sound  ====
 
−
Here is an example for using the speaker, based onthe following basic program:
 
−
 
−
<syntaxhighlight lang="basic">
 
−
; 50  POKE 768,V: POKE 769,P - 255 *  INT (P / 256): POKE 800,1 + P / 256
 
−
; 60  CALL 770: RETURN
 
−
; 95  FOR K = 1 TO N: READ V(K),P(K): NEXT K
 
−
; 100  FOR K = 1 TO N:V = V(K):P = P(K)
 
−
; 110  GOSUB 50
 
−
;!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
 
−
</syntaxhighlight>
 
−
 
−
<syntaxhighlight lang="6502">
 
−
*=$6000
 
−
!to "HL.bin", plain ; set output file and format
 
−
!cpu 6502 ; set processor type
 
−
 
−
;start
 
−
; 95  FOR K = 1 TO N: READ V(K),P(K): NEXT K
 
−
; 100  FOR K = 1 TO N:V = V(K):P = P(K)
 
−
ini:
 
−
lda #70
 
−
sta cnt+1
 
−
lda #music&255
 
−
sta gotbyte+1
 
−
lda #music/256
 
−
sta gotbyte+2
 
−
 
−
lop:
 
−
;V
 
−
jsr gotbyte
 
−
sta L300
 
−
jsr gotbyte
 
−
;P
 
−
jsr gotbyte
 
−
sta L301
 
−
jsr gotbyte
 
−
clc
 
−
adc #1
 
−
sta L320
 
−
jsr beep
 
−
 
−
dec cnt+1
 
−
cnt lda #70
 
−
bne lop
 
−
; 110  GOSUB 50
 
−
; 50  POKE 768,V: POKE 769,P - 255 *  INT (P / 256): POKE 800,1 + P / 256
 
−
; 60  CALL 770: RETURN
 
−
jmp ini
 
−
gotbyte
 
−
lda music
 
−
inc gotbyte+1
 
−
bne noinch
 
−
inc gotbyte+2
 
−
noinch
 
−
rts
 
−
;!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
 
−
beep:
 
−
ldy #1
 
−
ldx #1
 
−
loc_302:
 
−
LDA $C030
 
−
 
−
loc_305:
 
−
DEY
 
−
BNE loc_30D
 
−
DEC L301
 
−
loc_30B:
 
−
BEQ loc_316
 
−
 
−
loc_30D:
 
−
DEX
 
−
BNE loc_305
 
−
LDX L300
 
−
JMP loc_302
 
−
loc_316:
 
−
DEC L320
 
−
BNE loc_30B
 
−
RTS
 
−
L301 !byte 0
 
−
L300 !byte 0
 
−
L320 !byte 0
 
−
music
 
−
!word 76,192,85,64,96,64,102,64,114,128,114,64,96,64,102,64,114,64,128,64
 
−
!word 114,64,152,64,171,64,152,512,76,192,85,64,96,64,102,64,114,128,114,64
 
−
!word 96,64,102,64,114,64,128,64,114,64,152,64,171,64,152,512,85,64,85,64
 
−
!word 85,64,96,64,144,128,144,64,128,64,76,128,85,64,96,64,144,128,114,64
 
−
!word 96,64,102,128,114,64,128,64,128,128,114,64,128,64,114,512,85,64,85,64
 
−
!word 85,64,96,64,144,128,144,64,128,64,76,128,85,64,96,64,144,128,114,64
 
−
!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

Latest revision as of 12:55, 8 April 2024

Introduction

Wanting to start sizecoding on a 6502 platform in this day and age can be tough.

6502.jpg

So here is a bit of help to get you started:

The 6502 processor

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.

Adressing modes

To be added.

Zero page

When using the 6502 for sizecoding, you'll mostly be working from zeropage

6502 Based Platforms

Generic 6502 sinus table generator

	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

General 6502 Resources

Retrieved from "http://www.sizecoding.org/index.php?title=6502&oldid=1399"