ROM programming
The ATW800/2 for the Mega ST bus features two flash ROMs that provide space for four 256 KB TOS images.
The DIP switch at the back of the card can select these ROMs. Looking at the DIP switch from the back of the card, the switches read 1 and 2 from left to right:
| Slot # | Sw1 | Sw2 | Default ROM |
|---|---|---|---|
| 1 | Down | Down | TOS 2.06 |
| 2 | Up | Down | Latest EMU TOS |
| 3 | Down | Up | Previous EMU TOS version |
| 4 | Up | Up | TOS 1.04 |
Disabling the ROMs
Depending on your board revision there are diffrent ways to disable the onboard TOS ROM.
Revision 1.1b and later
Owners of the most recent card revisions can simply pull the jumper marked with “ROM enable” on the card.
Revision 1.1a
Owners of ATW800/2 with a revision of 1.1a can also use this red jumper but also need to do a tiny little bit of soldering. Due to a design mistake, the left pin of the jumper needs a connection to a 5V source. This is for example available at the 3rd pin from right of TRAM socket “SLOT 2” using a jumper wire on the backside of the card.
Revisions previous to 1.1a
Owners of the early card revisions need to physically remove the ROM chips from their sockets.
You can do this by using either a dedicated PLCC pulling tool (shown below on the left) or a thin but sturdy tool and carefully sticking it into the notches in the corners of the socket one side at a time. Gently remove the ROM chip by lifting it up a little on each side. After a couple of lifts, it will pop out.
The PLCC package was intentionally chosen because this allows removing the ROM chips and external programming by using an EPROM burner/programmer/"blower".
That said, the PLCC sockets are not made for lots of insertions and removals and will wear out pretty quickly.
So try to keep the number of in's and out's as low as possible!
Programming the ROMs
👉 The standard way to program the ROMs is in-system using the flash ROM called FLASHATW.TTP, which you can find in the driver archive.
After downloading a suitable ROM image from, for example, from https://www.atariworld.org/tos-rom/ and saving it on your disk drive, start FLASHATW. Because it’s a TTP (TOS takes parameters), all you need to do is to enter the filename of your TOS ROM (e.g., tos206uk.img) and klick OK.
After the ROM image has loaded, you’ll see this screen:
It displays the detected TOS version of the loaded file as well as the currently running TOS version. After that, it prints the device information of the installed flash ROMs.
All you have to do then is acknowledge the process and wait a couple of seconds. The upper lines of the screen will flash for a while before the system resets itself and boots your newly programmed TOS. We recommend you boot your Mega ST into a native video mode (i.e., ST-High/Med) to do the programming. Running it when the ATW800/2 video-out is active might result in strange outputs.
| ❗Do not flash your ROMs when using an accelerator. Due to their caches, accelerators might corrupt the process, which could result in a broken ROM image ❗ |
Revive your ROM
If you screwed up a ROM (slot), there is a way to revive it:
- Switch to a different ROM slot by using the DIP switch.
- Reset and boot into the ROM you’ve just selected.
- Run a RAM EMU TOS as provided on the EMU TOS homepage download section (emutos-prg-1.x.zip).
- Running a RAM EMU TOS will automatically reset your system and boot into EMU TOS, which resides in RAM instead of ROM. Wait until the reboot is done.
- You can now safely switch the ROM DIP switches to the slot you have merciless destroyed before.
- Run the FLASHATW.TTP as explained before using a working ROM image.
- You can now cold reset your Mega ST and it should boot from the image you just programmed.
If nothing works anymore and you screwed up all four ROM images, there’s still a way to revive your system:
You will find two original ROM images on the public share in a folder called “Restore images,” which you can use for external programming. These images are available in case you screwed up all of your ROMs and can’t boot anymore.
You will need an external programmer (maybe an PLCC adapter) and remove the ROM chips to do this. High and low ROM are marked on the PCB.