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Re: Olivetti M20 emulation status? [Re: rfka01] #78964 05/10/12 10:56 PM
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R. Belmont Offline
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Ahh, nice. Thanks Duke, we'll make that work later then.

Re: Olivetti M20 emulation status? [Re: R. Belmont] #78968 05/11/12 06:45 AM
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Olivier Galibert Offline
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I think that's identical to what the sega model 1/2 sound boards do.

OG.

Re: Olivetti M20 emulation status? [Re: rfka01] #78970 05/11/12 08:45 AM
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z8001cpg Offline
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I also found this explanation after a hint from rfka01.
But I don't understand the "On completion of the program" part. It's the BIOS, it doesn't "complete". Maybe it's this: The first instruction in the BIOS is a "clrb 0x4ffff", so this should set A3 line and disable the mapping.

Re: Olivetti M20 emulation status? [Re: rfka01] #78978 05/11/12 12:47 PM
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R. Belmont Offline
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Yeah, that clrb 0x4ffff would certainly assert A3. That's likely what does it.

Re: Olivetti M20 emulation status? [Re: rfka01] #78979 05/11/12 02:41 PM
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Kale Offline
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What would be annoying about the z8001 is the MMU stuff, I've snuffed the trap -> give up when I've skellized the driver (and afaik no SW is dumped anyway).

Re: Olivetti M20 emulation status? [Re: rfka01] #78980 05/11/12 02:49 PM
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I think if we can walk him through the MESS-specific bits Christian is the guy to do it though - he seems to be very knowledgeable about the M20.

Re: Olivetti M20 emulation status? [Re: rfka01] #78993 05/11/12 10:21 PM
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z8001cpg Offline
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Ok, now my problem is not the M20 or Z8000, but MESS :-)

The emulation passes the memory test, but the BIOS stops with

E C0

which means, 8255 (printer) interface failed.

I've tried the best part of this evening to add a 8255 to the m20 driver, but failed miserably.

If someone could explain to me how to add it, please do.

The 8255 in the M20 is mapped to the following I/O addresses:

0x81 - Port A
0x83 - Port B
0x85 - Port C
0x87 - Control Port

Thanks,
chris

Re: Olivetti M20 emulation status? [Re: z8001cpg] #78995 05/12/12 02:36 AM
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Just Desserts Offline
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I can't really explain it better than the drivers that already have it implemented. Have you used pre-existing drivers that use the 8255, such as savia84.c, radio86.c, pc8801.c, pc9801.c, pc6001.c, fidelz80.c, and other drivers as reference? Each one seems to have its own more or less unique way of communicating with the 8255, perhaps one of them will suit your use case.

Re: Olivetti M20 emulation status? [Re: rfka01] #78996 05/12/12 02:50 AM
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I added the 8255 and the two 8251s (in SVN), but of course without any devices connected to them the BIOS tests still fail.

The use case here was kind of unusual - they skip addresses on the 8255 so it needed a custom hookup.

ETA: the 8255 test sets port A as input and expects it to return values written to it (test is at label L53 in the disassembly, address 0x4085C in the ROM); this is undocumented behavior of the 8255. Kale, or Carl, or anyone have any ideas? smile

Last edited by R. Belmont; 05/12/12 03:50 AM.
Re: Olivetti M20 emulation status? [Re: rfka01] #78999 05/12/12 06:20 AM
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Micko Offline
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Kale: if I am not mistaken you had issue in past with z80001 with tim011 driver, that one did not had any software we could found. It was computer used in schools but only in Belgrade and few other cities so I have to find if someone can provide us that.

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