Dumping/reverse engineering MSX models thread

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Por DamnedAngel

Master (248)

imagem de DamnedAngel

12-12-2021, 21:58

Hi All,

Are the dumps for Mitsubishi ML-8000 still needed? I just managed to lay my hands on one...

Best,
Dan

Por Manuel

Ascended (18955)

imagem de Manuel

12-12-2021, 23:37

Yes, they are. Thanks in advance!

Por sd_snatcher

Prophet (3552)

imagem de sd_snatcher

13-12-2021, 16:39

gdx wrote:

This method seems insufficient to me to know precisely the matrix.

But KEYMATR.BAS shows the exact location of each key you press on the keyboard matrix. What else would be needed to know it precisely?

I.e.: This is the result of the Y key being pressed on a Japanese keyboard:

Por Quasartfe

Supporter (12)

imagem de Quasartfe

31-01-2022, 13:44

hello , the link is offline .i need this rom

Por Quasartfe

Supporter (12)

imagem de Quasartfe

31-01-2022, 13:45

I need the vg8020/40 bios/rom but the links are down ...

Por Manuel

Ascended (18955)

imagem de Manuel

10-02-2022, 22:37

Manuel wrote:

Tabajara Labs was helping by dumping his Sanyo MPC-2/Wavy2. One peculiar thing he got: running SWIOSCAN.BAS (which tries to discover switched I/O devices) turned up with ID 135... Does anyone have an idea what this might be?

sdsnatcher wrote:

This is really pretty intriguing.

1) IDs greater than 127 are meant for devices, while IDs <=127 are meant for makers. But this machine doesn't seem to have any special hardware inside.

2) It could be the T7775 MSX-Engine, so maybe it has some special configuration options in the switched I/O ports. Have you run SWIOSCAN.BAS on any other machine that has this engine inside to check if they also return this ID?

Apparently the Mitsubishi ML-8000 also has Switched IO ID 135....

Por sdsnatcher73

Prophet (3532)

imagem de sdsnatcher73

11-02-2022, 04:11

In the ML-8000 I suspect it might be used for the ML-10KB keyboard. I have that keyboard and it does not work on any of my MSX’s. I have not tried it on the ML-8000 that just came in. Main reason is because the machine’s RAM is broken so I need to use a RAM cart (or multicart) to boot the machine. I’ll check it with a slot expander later.

Por Grauw

Ascended (10623)

imagem de Grauw

14-02-2022, 16:38

Manuel wrote:

Apparently the Mitsubishi ML-8000 also has Switched IO ID 135....

Could it be that this MSX1 has a floating bus, and thus happens to return 170 from the I/O read?

It does not look like SWIOSCAN.BAS does a detection for floating bus.

Por sdsnatcher73

Prophet (3532)

imagem de sdsnatcher73

14-02-2022, 18:14

Anything is possible on the first ever MSX Wink how can we determine if it has a floating bus? And would a floating bus lead to detection of port 135 or rather a random number?

Por Grauw

Ascended (10623)

imagem de Grauw

14-02-2022, 21:22

sdsnatcher73 wrote:

Anything is possible on the first ever MSX Wink

If it’s the first ever MSX then I’d say the odds of it having a floating bus are high, and the odds of it having expanded I/O are very low since the I/O space was still wide open and empty at that point. Not sure expanded I/O was even officially specified yet that early on.

sdsnatcher73 wrote:

How can we determine if it has a floating bus? And would a floating bus lead to detection of port 135 or rather a random number?

Just do ?INP(0) (or some other unused I/O port), and if it at any time gives any value other than 255, you know it’s a floating bus. If it has pull-ups it will be 255 and if it has pull-downs it will be 0 all the time (though I doubt anything has pull-downs since I believe it draws more power). A floating bus will give unpredictable results, though not necessarily random.

Specifically for the expanded I/O ports test, if you write 0 to 40H and read anything back other than 0FFH, it similarly indicates there is a floating bus. But of course it could be returning 0FFH by chance. So as the tester scans through all the device IDs, probably worth flagging how many of those return a non-0FFH result in addition to which it does return the exact complement for. Then if those numbers don’t add up you know the match is probably a coincidence.

By the way, I think it is valuable documenting which machines have a floating bus, and emulating it.

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