Various pre-requisites

To get better syntax highlighting for 6502 assembler I found a vim syntax file asmM6502.vim

https://github.com/jestin/asmM6502.vim

This was saved as ~/.vim/syntax/asmM6502.vim

To make sure assembler source code used the 6502 syntax add:

autocmd BufRead,BufNewFile *.s,*.asm,*.inc set filetype=asmM6502

to ~/.vimrc

To compile source to machine-code suitable for blowing onto EEPROM use the vasm compiler

It's possible to self-compile VASM by downloading the source-code from:

http://sun.hasenbraten.de/vasm/

but there are ready made binaries here, specifically for the 6502 old-style binaries:

http://www.compilers.de/vasm.html

Use the link at the foot of the page:

http://www.ibaug.de/vasm/vasm6502.zip

Download, unzip (extracts the files needed into ../vasm6502_oldstyle/linux/)

sudo cp ./vasm6502_oldstyle/linux/* /usr/local/bin

Add an alias to ~/.bashrc

alias vasm='vasm6502_oldstyle -Fbin -dotdir'

for the most used options

To compile a source file to a binary a.out file:

vasm hello_world.s

hello_world.s

PORTB = $6000
PORTA = $6001
DDRB = $6002
DDRA = $6003
 
E  = %10000000
RW = %01000000
RS = %00100000
 
  .org $8000
 
reset:
  ldx #$ff
  txs
 
  lda #%11111111 ; Set all pins on port B to output
  sta DDRB
  lda #%11100000 ; Set top 3 pins on port A to output
  sta DDRA
 
  lda #%00111000 ; Set 8-bit mode; 2-line display; 5x8 font
  jsr lcd_instruction
  lda #%00001110 ; Display on; cursor on; blink off
  jsr lcd_instruction
  lda #%00000110 ; Increment and shift cursor; don't shift display
  jsr lcd_instruction
  lda #$00000001 ; Clear display
  jsr lcd_instruction
 
  ldx #0
print:
  lda message,x
  beq loop
  jsr print_char
  inx
  jmp print
 
loop:
  jmp loop
 
message: .asciiz "Hello, world!"
 
lcd_wait:
  pha
  lda #%00000000  ; Port B is input
  sta DDRB
lcdbusy:
  lda #RW
  sta PORTA
  lda #(RW | E)
  sta PORTA
  lda PORTB
  and #%10000000
  bne lcdbusy
 
  lda #RW
  sta PORTA
  lda #%11111111  ; Port B is output
  sta DDRB
  pla
  rts
 
lcd_instruction:
  jsr lcd_wait
  sta PORTB
  lda #0         ; Clear RS/RW/E bits
  sta PORTA
  lda #E         ; Set E bit to send instruction
  sta PORTA
  lda #0         ; Clear RS/RW/E bits
  sta PORTA
  rts
 
print_char:
  jsr lcd_wait
  sta PORTB
  lda #RS         ; Set RS; Clear RW/E bits
  sta PORTA
  lda #(RS | E)   ; Set E bit to send instruction
  sta PORTA
  lda #RS         ; Clear E bits
  sta PORTA
  rts
 
  .org $fffc
  .word reset
  .word $0000

gm4slv@laptop:~/6502 $ vasm hello_world.s
vasm 1.8h (c) in 2002-2019 Volker Barthelmann
vasm 6502 cpu backend 0.8 (c) 2002,2006,2008-2012,2014-2018 Frank Wille
vasm oldstyle syntax module 0.13f (c) 2002-2018 Frank Wille
vasm binary output module 1.8a (c) 2002-2009,2013,2015,2017 Volker Barthelmann
 
seg8000(acrwx1):                 143 bytes
segfffc(acrwx1):                   4 bytes

Inspect the hexcode in the binary file hexdump

gm4slv@laptop:~/6502 $ hexdump -C a.out
00000000  a2 ff 9a a9 ff 8d 02 60  a9 e0 8d 03 60 a9 38 20  |.......`....`.8 |
00000010  63 80 a9 0e 20 63 80 a9  06 20 63 80 a9 01 20 63  |c... c... c... c|
00000020  80 a2 00 bd 32 80 f0 07  20 79 80 e8 4c 23 80 4c  |....2... y..L#.L|
00000030  2f 80 48 65 6c 6c 6f 2c  20 77 6f 72 6c 64 21 00  |/.Hello, world!.|
00000040  48 a9 00 8d 02 60 a9 40  8d 01 60 a9 c0 8d 01 60  |H....`.@..`....`|
00000050  ad 00 60 29 80 d0 ef a9  40 8d 01 60 a9 ff 8d 02  |..`)....@..`....|
00000060  60 68 60 20 40 80 8d 00  60 a9 00 8d 01 60 a9 80  |`h` @...`....`..|
00000070  8d 01 60 a9 00 8d 01 60  60 20 40 80 8d 00 60 a9  |..`....`` @...`.|
00000080  20 8d 01 60 a9 a0 8d 01  60 a9 20 8d 01 60 60 00  | ..`....`. ..``.|
00000090  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00007ff0  00 00 00 00 00 00 00 00  00 00 00 00 00 80 00 00  |................|
00008000

An open source project minipro to use the TI866 USB EEPROM programmer under Linux

git clone https://gitlab.com/DavidGriffith/minipro.git
cd minipro
make
sudo make install

to burn an EEPROM

minipro -p AT28C256 -w a.out

— John Pumford-Green 10/08/22 13:50

• Sept' 2022 : Moved to CA65 assembler.

CA65 Setup