Home Page Forums MAME MAME Writing a driver from scratch - help, please

Hello,

I write again because I am currently repairing the Datamaster of a colleague and he has a different romset than mine, so I would like to make it known that I will be adding it when the ROMs are dumped. I think I have other romsets too, so I'll be complimenting the work with them, too.

Having received a second keyboard and a second floppy controller during this process makes it possible to add a second floppy controller code and opens the possibility to dump the floppy disk microcontroller code too.

EDIT:
The keyboard is AZERTY!

Have a nice day!

Hello,

I managed to repair the computer enough for it to display the diagnostics codes, but it gets stuck at test 05h (8275 + 8257). Therefore, I have an important conclusion that will affect the emulation at its core. I have detected a difference in the behaviour of the stock 8275 respect the Datamaster's one respect the interrupts. This means I will have to roll back some of the changes I made in the 8275 device. At the same time, I will have to add another one with the expected behaviour of the Datamaster's CRTC. As I haven't created a variant device yet, do you know if it is hard to do?

EDIT:
Another Datamaster will be coming my way soon, so I will be able to add even more features. This one will be mine, unlike the one I am currently repairing.

EDIT 2:
I am having to patch ROS 02h to rewrite test 05 for compatibility with the stock devices. Could I ask for some help to do so?

EDIT 3:
I have corrected the 8275 device, added the IBM CRTC, and created a second machine with the stock 8275.

Thank you in advance!

Hello,

This is to clarify and correct a few statements I made in the last post.
A Datamaster set of boards arrived yesterday from USA. The computer mostly works, or at least is working more than the French Datamaster I am repairing. I have been able to conduct some tests on the American unit. Apparently my claims that the IBM CRTC is different from the stock 8275 is wrong. The American motherboard accepted the stock 8275 and even the Soviet KR580VG75. This means that I will have to roll back the latest changes and restore the previous values. This means that there is no value for the second emulated machine I made, other than for testing purposes with a 8276, but even that could be made with a single emulated machine running a virtual 8275.

Thank you very much!

I have news that could expand the development of this emulated machine further.

• In the first place, I was able to test a French keyboard on my Spanish model and found that the keycodes remain the same, their translation depends exclusively of the configuration switches of the computer.
• Also, the microcontroller at the disk drive controller card has been successfully identified as 8048 and dumped. Maybe it is time to start studying the card.
• A package of dumps will be archived during what remains of this week and therefore will contain the first full set of a Datamaster ever dumped (my last version lacked the floppy controller). It will also contain different versions of the firmware. This will be the largest package of Datamaster firmware to be released to this date.
• In a few weeks I may receive a package of leased boards to dump and study. I don't own these boards, therefore it will bring in new data to my research and more expansions to the machine.

In light of these new developments, I may be able not only to continue the development of my current machine, but to force it to implement interfaces such as the expansion bus.

Thank you for all your support all this time!

I have acquired a word-editor card. When I receive it, I will study it in order to bring it to MAME.

I am thinking about the word-processing card, and it will be a challenge for me. In the first place, it is an optional device, so it will require the pre-ISA bus to be defined. In the second place, it contains a second 8275 CRTC so it means it will generate a "second screen". Finally, that it intercepts the video signal of the motherboard and possibly disables it to supplant it with the second field generated by the auxiliary CRTC. I know there will be some time before this piece of hardware reaches me, but I would like to have some idea of how to treat it when it arrives. Please, could anybody give me some piece of advice or guides on how to proceed with the foresaid stuff?

Thank you in advance!

The biggest lift there is going to be just defining and attaching the bus. Does this card completely replace the motherboard's video or overlay it? Taking completely over a system's built-in video from a bus card is very doable, I just did it in 0.277.

I still don't know, the part still has to arrive. Still, considering it has an independent clock from the motherboard I don't think it overlays, but replaces it.

Yesterday I found I/O ports for the NEC 765 and a 8255 in the Floppy disk controller card.
How would I have to do to define the bus, please? This way I could start with the development of the FDC card.

Thank you in advance!