Tag Archives: C64

C64 PRG to cartridge.

I’ve got the tools and Bigred made me enthusiastic again.
My goal is to make a C64 Cartridge from a PRG. And Not any program, it is the 8085 Emulator from Sepp.

Serveral problems i have to ‘fix’

  • The program is 17K, Cartridges can only be 16K.
    So i have to use 2x 8K and compress the data.
    This means it have to be uncompressed at start time.
    ( I was thinking of using exomiser for this )
  • Program starts normally at $0820 and probably is not optimised to run anywhere else.
    So a starting routine has to copy the program from cartridge memory to the correct location

Luckily i have the source! How cool is that

For version 4.73 it states : Starting at $0820 .. but my hexdump is off by one??!?

root@battlestation:/home/fash/Projects/minipro# hexdump -C /tmp/8085.prg  | head
00000000  01 08 1e 08 c5 07 9e 32  30 38 30 20 42 59 20 4d  |.......2080 BY M|
00000010  41 52 54 49 4e 20 4d 45  59 45 52 49 4e 4b 00 00  |ARTIN MEYERINK..|
00000020  00 20 ec 08 20 7f 19 20  2b 2c 20 11 19 20 b8 08  |. .. .. +, .. ..|
00000030  20 20 2c 20 a0 2c 20 f2  2c 20 11 e1 4c 00 15 aa  |  , ., ., ..L...|
00000040  aa a2 06 ad b7 08 9d 48  d8 bd 48 04 20 88 39 9d  |.......H..H. .9.|
00000050  48 04 ca 10 ee a9 60 8d  4c 04 4c 50 47 00 a9 d0  |H.....`.L.LPG...|
00000060  2c a9 f0 8d 45 1f 4c 11  e1 1e 93 0d 20 20 4d 41  |,...E.L.....  MA|
00000070  52 54 49 4e 20 4d 45 59  45 52 49 4e 4b 27 53 0d  |RTIN MEYERINK'S.|
00000080  0d 20 38 30 38 35 20 45  4d 55 4c 41 54 4f 52 20  |. 8085 EMULATOR |
00000090  20 56 34 2e 38 30 0d 0d  20 20 28 43 29 20 31 20  | V4.80..  (C) 1 |

00000020 00 20 ec starts with 00 at $0020 .. and not 20 ?!?!

Tools used until now:

  • Vice – C64 Emulator
    x64 -cartcrt 8085.crt
  • c1541 – Linux disk tool for C64 images.
    Used this to extract the 8085emulator PRG
  • prg2crt.py – a convertor from PRG to a cartrid file which can be used by Vice
    python2 prg2crt.py 8085.prg 8085.crt
  • minipro – eeprom programming tool for Linux
    minipro -p AT28C64 -w /tmp/test.bin
  • cartconv (tool from vice to convert crt <-> bin)
    cartconv -t normal -i test.bin -n ‘my cart’ -o test.crt
  • xa – Cross assembler 65xx/R65C02/65816
  • ACME – the ACME Crossassembler for Multiple Environments
Memory Map C64 – source c64-wiki.com

Card Low starts at $8000, so that’s the place where those roms are going to be.
To place on this address:

Copy routine : from ($8000 + this copy routine) to $0820
When to decompress??
jmp routine to $0820

A cartridge file >16K and with his emulation headers seems to work??!

Also nice: Magic Desk Cartridge Generator V3.0

UPDATE: 20220811

exomizer sfx 0x0820 8085.prg -o data.exo # Compress and start at 0x0820 
xa frame.asm -o frame.bin # Add code and write binary
x64 --cart16 frame.bin # Test cartridge with Vice

frame.asm

;---------------------------------------------------------- 
; example usage
; xa frame.asm -o frame.bin
; cartconv -t normal -i frame.bin -n 'my cart' -o frame.crt
; x64 -cartcrt frame.crt
;----------------------------------------------------------

;no load-adress for bin-file, so no header here

*=$8000
.word launcher ;cold start
.word launcher ;warm start
.byte $c3	;c
.byte $c2	;b
.byte $cd	;m
.byte $38	;8
.byte $30	;0

launcher
  stx $d016
  jsr $fda3	;prepare irq
  jsr $fd50	;init memory
  jsr $fd15	;init i/o
  jsr $ff5b	;init video
                ;make sure this sets up everything you need,
                ;the calls above are probably sufficient
  ldx #$fb
  txs

;set up starting code outside of cartridge-area
move_starter
  ldx #(starter_end-starter_start)
loop1
  lda starter_start,x
  sta $100,x
  dex
  bpl loop1
  jmp $100
;---------------------------------
starter_start	
  ldx #$40 ;64 pages = 256 * 64 = 16384 Bytes
  ldy #0
loop
src
  lda exomized_data,y
dst
  sta $801,y
  iny
  bne loop
  inc src+2-starter_start+$100 
  inc dst+2-starter_start+$100
  dex
  bpl loop

;make sure settings for $01 and IRQ etc are correct for your code
;remember THIS table from AAY64:

;       Bit+-------------+-----------+------------+
;       210| $8000-$BFFF |$D000-$DFFF|$E000-$FFFF |
;  +---+---+-------------+-----------+------------+
;  | 7 |111| Cart.+Basic |    I/O    | Kernal ROM |
;  +---+---+-------------+-----------+------------+
;  | 6 |110|     RAM     |    I/O    | Kernal ROM |
;  +---+---+-------------+-----------+------------+
;  | 5 |101|     RAM     |    I/O    |    RAM     |
;  +---+---+-------------+-----------+------------+
;  | 4 |100|     RAM     |    RAM    |    RAM     |
;  +---+---+-------------+-----------+------------+
;  | 3 |011| Cart.+Basic | Char. ROM | Kernal ROM |
;  +---+---+-------------+-----------+------------+
;  | 2 |010|     RAM     | Char. ROM | Kernal ROM |
;  +---+---+-------------+-----------+------------+
;  | 1 |001|     RAM     | Char. ROM |    RAM     |
;  +---+---+-------------+-----------+------------+
;  | 0 |000|     RAM     |    RAM    |    RAM     |
;  +---+---+-------------+-----------+------------+

  lda #$35 ;cart is always on instead of BASIC unless it can be switched off via software
  sta $01
  jmp $80d ;for exomizer, i.e.

starter_end
;----------------------------------
exomized_data
.bin 2,0,"data.exo"
;syntax for exomizer 2.0.1:
;exomizer sfx sys game.prg -o data.exo
main_file_end
;fill up full $4000 bytes for bin file ($c000-$8000=$4000)
.dsb ($c000-main_file_end),0

Exomiser info

 Reading "8085.prg", loading from $0801 to $4CE9.
 Crunching from $0801 to $4CE9.
Phase 1: Instrumenting file
-----------------------------
 Length of indata: 17640 bytes.
 [building.directed.acyclic.graph.building.directed.acyclic.graph.]
 Instrumenting file, done.

Phase 2: Calculating encoding
-----------------------------
 pass 1: optimizing ..
 [finding.shortest.path.finding.shortest.path.finding.shortest.pat]
  size 80273.0 bits ~10035 bytes
 pass 2: optimizing ..
 [finding.shortest.path.finding.shortest.path.finding.shortest.pat]
  size 80039.0 bits ~10005 bytes
 pass 3: optimizing ..
 Calculating encoding, done.

Phase 3: Generating output file
------------------------------
 Encoding: 1101112133423160,1122,2010223445667788,032144406789BBCD
 Length of crunched data: 10034 bytes.
 Crunched data reduced 7606 bytes (43.12%)
 Target is self-decrunching C64 executable,
 jmp address $0820.
 Writing "data.exo" as prg, saving from $0801 to $304C.
Memory layout:   |Start |End   |
 Crunched data   | $07E7| $2F18|
 Decrunched data | $0801| $4CE9|
 Decrunch table  | $0334| $03D0|
 Decruncher      | $00FD| $01C0| and $9F,$A7,$AE,$AF
 Decrunch effect writes to $DBE7.
Decruncher:  |Enter |During|Exit  |
 RAM config  |   $37|   $37|   $37|
 IRQ enabled |     1|     1|     1|