Atari ST cartridge port

[ppera]

Usage of cartridge port on Atari ST machines as is originally intended - for fast accessing some short utilities and programs is probably little obsolete now. But, because I don't see that it is much covered, I will give here required informatons how to add applications on cartridge port. In second part HW will be covered: how to making cartridge board.

Cartridge port uses address range: $FA0000-$FBFFFF, it is 128KB, not much these days. But we may put there several short apps. especially if we compress them (SFX). Port is read only. At beginning magic long value $ABCDEF42 means that cartridge is active, and has at least 1 programm on. (For diagnostic cartridges we have different magic, but will not deal here with..) After it comes header of first program - see attached pic about header.

CA_NEXT points to header of next program, or has value 0 if no more.

CA_INIT holds address of optional init. routine. Bits 24-31 aren't used for addressing, and ensure in which moment by system init prg. will be initialized and/or started. Bits have following meanings, 1 means execution:

bit 24: Init. or start of cartridge SW after succesfull HW init. System variables and vectors are set, screen is set, Interrupts are disabled - level 7.

bit 25: As by bit 24, but right after enabling interrupts on level 3. Before GEMDOS init.

bit 26: System init is done until setting screen resolution. Otherwise as bit 24.

bit 27: After GEMDOS init. Before booting from disks.

bit 28: -

bit 29: Program is desktop accessory - ACC .

bit 30: TOS application .

bit 31: TTP .



CA_RUN: Program start address. All optional inits are done before. This is required only if program runs under GEMDOS.

CA_TIME and CA_DATE: File's time and date stamps. In GEMDOS format.

CA_SIZE: Lenght of app. in bytes. Not really used.

CA_NAME: DOS/TOS filename 8.3 format. Terminated with 0 .


Cartridge programs for GEMDOS will appear on desktop in virtual drive c: (lowcase c) .

There are some limitations: only executables are accessible on cartridge - it means that PRG with separated RSC file will not work. Programs must be written so, that run from ROM. This latest is fortunately easy to override, what is important, because we want to put there some existing programs, written to run from RAM. I will give here simple code example, which copies and relocates executables from ROM to RAM.

Code: Select all

*Multi Cartridge programm starter

*Rom cartridge

  org $FA0000

  dc.l $abcdef42 *magic
  dc.l second
  dc.l 0
  dc.l run1
  dc.w $a5CD *time
  dc.w $1e28 *date
  dc.l 31420
  dc.b "MONC.PRG",0
    even

second
  dc.l third
  dc.l 0
  dc.l run2
  dc.w $b149 *time
  dc.w $1e51 *date
  dc.l 7961
  dc.b "FIRDC.PRG",0
  even

third
  dc.l 0
  dc.l 0
  dc.l coac
  dc.w $a5CD *time
  dc.w $1e28 *date
  dc.l 22568
  dc.b "DISKDOCT.PRG",0
  even

*Input: a6-progbase adress, d2- len/4

coac  lea thecoac(pc),a6
  move.w #22568/4,d2
  bra.s common


run1  lea themon(pc),a6
  move.w #31420/4,d2
  bra.s common


run2  lea thefirdc(pc),a6
  move.w #7961/4,d2

*test free ram

common  move.l 4(sp),a0 *tpa begin
  move.l 4(a0),d0 *tpa end
  sub.l a0,d0 *available len
 
  moveq #0,d1
  add.l 2(a6),d1 *text len
  add.l 6(a6),d1 *data len
  add.l 10(a6),d1 *bss len
  add.l #512,d1 *for basepage+reserve
 
*d1 now holds needed ram len

  cmp.l d1,d0
  bmi.s noram

  lea 256(a0),a1
  move.l a1,8(a0)  *txt beg (startadress of prg) 

  lea -28(a1),a2
  move.l a2,a3 *store beginadr of header
     
*copy code
ccl move.l (a6)+,(a2)+ 
  dbf d2,ccl
 


*Relocation
*a0 is base page,a1 is text begin, a3 is header addr.

   move.l a1,a2
   add.l 2(a3),a2  *txt len
   add.l 6(a3),a2  *data len
   move.l a1,d0
   tst.l (a2)
   beq.s corrbp
   ADDA.L   (A2)+,A1
   clr.l d1
relol   ADD.L   D0,(A1)
bigd   
   MOVE.B   (A2)+,D1
   beq.s corrbp
   CMP.B   #1,D1
   bne.s   nmd
   ADDA.W   #$FE,A1
   BRA.S   bigd
nmd   ADDA.L   D1,A1
   BRA.S   relol
corrbp
   MOVE.L   2(A3),$C(A0)
   MOVE.L   6(A3),$14(A0)
   MOVE.L   $A(A3),$1C(A0)
   MOVE.L   $C(A0),D1
   ADD.L   D0,D1
   MOVE.L   D1,$10(A0)
   ADD.L   $14(A0),D1
   MOVE.L   D1,$18(A0)

   move.l d0,a1
   
   jmp (a1)
   
noram  pea mess(pc)
  move.w #9,-(sp)
  trap #1
  addq.l #6,sp
 
  move.w #1,-(sp) *wait keypress
  trap #1
  addq.l #6,sp
       
  clr.w -(sp)
  trap #1 *exit
 
mess dc.b 13,10,"Insufficient RAM !",0
  even

thecoac
  incbin DISKDOCT.PRG
 
   even
   dc.l 0,0 *gap

thefirdc
  incbin FIRDC.PRG
 
   even
   dc.l 0,0 *gap

themon
  incbin MONC.PRG

  even
   dc.l 0,0 *gap



Executables may be compressed to save space - for instance with PRG FIRDC on this cartridge example.

In attachment CART1.ZIP is this source and 64KB cartridge content - binary, and splitted to Low and High parts for EPROM burners.
You may play with binary in Hatari emulator, but first expand it to full 128KB, otherwise will not activate (for instance use DOS copy command: copy /b ca3f_1w.bin + ca3f_1w.bin cart.bin - will get 128KB ).
In Steem cartridge image file format is little different, as I see it adds four zeros at beginning... Right. Attachment CARD2.ZIP holds special cartridge SW, which creates RAMdisk C at boot. I included some disk utilities, control.acc in example. Cartridge image is in STC format, what is just regular binary with 4 zeros at start. So, you may play with it in Steem, or burn it for cartridge if strip those 4 zeros and split it...

[ppera]

Second part: HW

Original Atari cartridge design is for 4x 32KB (27C256) EPROMs. It is not wise this days, so we go on using 2x 64KB chips.
You may DL Eagle schematics and PCB designs in attachments - there is little simpler board with max 64KB too. Thanks to popsel for board designs...

Here may DL some diagnostic cartridge ROM contents for diverse Atari machines. Sizes are usually 64KB :
http://www.hobby-electronique.com/Proje ... fault.aspx

Note for schematics: address lines are shifted by 1 - it means that you need to connect A1 from port with A0 of EPROMs. A2 with A1 of EPROMs ets... On 128K version A15 of EPROMs is connected with ROM4. Of course, it is visible in Eagle files.

[techie_alison]

Keep it coming Ppera.

The bit I'm interested in is getting PRGs onto EPROMS. As in existing programs (that I can't change or recompile). Where do they go etc. etc. I have EPROMs and a burner, just how to get the images ready etc. etc.

Edge connectors are 2mm (and difficult to source) just to chip in here. The male ones aren't a problem since you can etch them.

[nativ]

I do believe I had a Rom called backpack -computer concepts, that generated a Rsc or similar file. It is a vague recolection, but may be possible?

Ashley

[techie_alison]

This is the board from a Fast Basic Cartridge, which provides utilities on drive 'c' (lower case, cartridge port) on the desktop.

It contains two 64Kbyte EPROMS, 27C512's.

[Heavy Stylus]

This is the board from a Fast Basic Cartridge, which provides utilities on drive 'c' (lower case, cartridge port) on the desktop.

It contains two 64Kbyte EPROMS, 27C512's.

Ignoring the spam above, I'd be really interested to know if it is possible to create clones of this board with the 'c' drive containing your own programs. This would potentially mean that you could create a 128KB game cartridge for the ST, which although some will argue it would be pointless, I think it could be quite fun.

I've been selling new C64 cartridges via RGCD for a while now, and it would be great if a new game from someone like paradize could be made in cartridge form for the STE - it would be really collectable IMO.

Do any cartridges auto-boot their contents?

[PaulB]

AFAIK the cartridge port is checked before the floppy or hard drive. If you have an auto folder on c and your program is in it, it can auto boot. Although the same problems exist with GEM not being booted so early so is has to be a TOS program that doesn't use GEM.

[ppera]

...really interested to know if it is possible to create clones of this board with the 'c' drive containing your own programs. This would potentially mean that you could create a 128KB game cartridge for the ST, which although some will argue it would be pointless, I think it could be quite fun.
I've been selling new C64 cartridges via RGCD for a while now, and it would be great if a new game from someone like paradize could be made in cartridge form for the STE - it would be really collectable IMO.
Do any cartridges auto-boot their contents?

Autoboot is possible in several points at system startup. As is described here at top. If game uses not GEM, may easily autoboot. With little compression you may put more than 128KB on cartridge.
But I think that autoboot is not so relevant. Actually, it will practically block machine from regular usage. Except that game can be exited to Desktop.

[simbo]

you can very easily make banks of 512k and use this for apps

you can have quite a few
you just need a small auto folder program that runs after an inital load
the cart supplies a magic number on boot and setup up a few events
and the auto program creates a menu by reseting to another section of the bootup rom on your cart
an mcu on the cart is setup to now decode which app is required
becouse while the banks and roms signals are being decoded also by the mcu
it decides which chips are read and when

and running the second part of the cart app {triggered by the now resident auto app}
this way you can load several big multiblocks
the block's of which are reloaded also by the auto folder prg
will work with some things even games ...
ive seen a guide to do this on vezz site..