C64_SKILLS/references/c64-quick-reference.md

Commodore 64 Quick Reference

Memory map overview

Range	Meaning
$0000-$00FF	Page zero: BASIC/KERNAL workspace, pointers, fast addressing
$0100-$01FF	Processor stack
$0200-$03FF	System workspace, buffers, vectors
$0400-$07E7	Default screen RAM
$07F8-$07FF	Default sprite pointers
$0801	Default BASIC program start
$A000-$BFFF	BASIC ROM, RAM underneath
$C000-$CFFF	Free RAM often used for ML routines
$D000-$DFFF	I/O, color RAM, character ROM, or RAM depending on banking
$E000-$FFFF	KERNAL ROM, RAM underneath

Common addresses

Dec	Hex	Name
1	$0001	6510 memory banking port
43	$002B	BASIC start pointer low
44	$002C	BASIC start pointer high
55	$0037	BASIC top pointer low
56	$0038	BASIC top pointer high
198	$00C6	Keyboard buffer count
646	$0286	Current text color
780	$030C	SYS A register save/pass
781	$030D	SYS X register save/pass
782	$030E	SYS Y register save/pass
783	$030F	SYS status save/pass
788	$0314	IRQ vector low
789	$0315	IRQ vector high
792	$0318	NMI vector low
793	$0319	NMI vector high
1024	$0400	Screen RAM
2040	$07F8	Sprite pointer 0
49152	$C000	Common ML start
53248	$D000	VIC-II base
53280	$D020	Border color
53281	$D021	Background color
54272	$D400	SID base
55296	$D800	Color RAM
56320	$DC00	CIA #1 base
56576	$DD00	CIA #2 base

KERNAL jump table

Hex	Routine	Purpose
$FF81	CINT	Initialize screen editor
$FF84	IOINIT	Initialize I/O
$FF87	RAMTAS	RAM test/init
$FF8A	RESTOR	Restore vectors
$FF8D	VECTOR	Read/set vectors
$FF90	SETMSG	Set system message flag
$FF93	SECOND	Send secondary address after LISTEN
$FF96	TKSA	Send secondary address after TALK
$FF99	MEMTOP	Read/set top of memory
$FF9C	MEMBOT	Read/set bottom of memory
$FF9F	SCNKEY	Scan keyboard
$FFA2	SETTMO	Set timeout
$FFA5	ACPTR	Read serial byte
$FFA8	CIOUT	Write serial byte
$FFAB	UNTLK	Untalk
$FFAE	UNLSN	Unlisten
$FFB1	LISTEN	Listen
$FFB4	TALK	Talk
$FFB7	READST	Read status
$FFBA	SETLFS	Set logical file/device/secondary address
$FFBD	SETNAM	Set filename
$FFC0	OPEN	Open file
$FFC3	CLOSE	Close file
$FFC6	CHKIN	Set input channel
$FFC9	CHKOUT	Set output channel
$FFCC	CLRCHN	Restore default I/O
$FFCF	CHRIN	Input character
$FFD2	CHROUT	Output character
$FFD5	LOAD	Load from device
$FFD8	SAVE	Save to device
$FFDB	SETTIM	Set clock
$FFDE	RDTIM	Read clock
$FFE1	STOP	Check STOP key
$FFE4	GETIN	Get input character
$FFE7	CLALL	Close all files
$FFEA	UDTIM	Update clock
$FFED	SCREEN	Get screen dimensions
$FFF0	PLOT	Read/set cursor position
$FFF3	IOBASE	Return I/O base

Color codes

Code	Color
0	Black
1	White
2	Red
3	Cyan
4	Purple
5	Green
6	Blue
7	Yellow
8	Orange
9	Brown
10	Light red
11	Dark gray
12	Gray
13	Light green
14	Light blue
15	Light gray

BASIC snippets

REM BORDER AND BACKGROUND
POKE 53280,6:POKE 53281,0

REM PUT "A" AT UPPER LEFT AND COLOR IT RED
POKE 1024,1:POKE 55296,2

REM CALL MACHINE LANGUAGE AT $C000
SYS 49152