Toshiba HX 22

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By wernerkai

Champion (357)

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28-11-2011, 02:59

Hello,

Please, does anybody know if is there an schematic or service manual for Toshiba HX 22 ?

Thanks,

Werner

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By msxholder

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28-11-2011, 21:45

Not ever seen an service manual of Toshiba HX22 or HX22gb
only of an fs tm-1 Toshiba msx2

By Manuel

Ascended (19270)

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08-09-2012, 14:04

We're investigating the Toshiba HX-22 RS-232C implementation. At startup it reads bit 3 of port 0x82... but that bit is undocumented. Does anyone have a schematic or other info that could clarify this?

What the ROM does: in a loop (100 iterations) toggle bits 0,3 of port #82 (write) and it expects to see bit 3 of port #82 (read) to toggle as well.

By RetroTechie

Paragon (1563)

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08-09-2012, 15:34

Can you make a high-res photo of the mainboard? That will show what IC's are in the machine, and probably make it easy to determine what IC's provide the RS-232 function. With the ROMs in hand, it shouldn't be hard to figure out how those IC's are attached to the machine (what I/O ports, for example). Btw: ROM dumps online somewhere?

Sometimes signals don't go 'through' such IC's, and are implemented using some separate glue logic. In which case you'd have to check schematic / trace those motherboard connections to find out what does what. But that's the exception rather than the rule.

Compare with the VDP... What you need to know is that it's a TMS9918 compatible (or V9938 etc), and that it's addressed through I/O ports 98/99h. From there on, a VDP databook has all the relevant info.

By Manuel

Ascended (19270)

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08-09-2012, 16:58

We have detailed photos and ROMs. But that doesn't make it clear yet what that bit 3 should do on port 0x82... unless you can see stuff we can't Smile

If you like I can get you those photos, do you mind coming to IRC for that? It provides easy file transfer.

By RetroTechie

Paragon (1563)

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08-09-2012, 18:59

Just mail those photo's please? (and RS-232 ROM) E-mail is in my user profile.

What you could see from that is what IC datasheet to grab (and then check the ROM how that IC's registers are used). Also try running MSXMEM. Machines with built-in RS-232 sometimes have a small buffer RAM in their memory map, maybe it shows up in MSXMEM output.

By Manuel

Ascended (19270)

Manuel's picture

08-09-2012, 21:14

Do you like to get 15MB of mail?

MSXMEM doesn't detect RAM of RS-232C interfaces. The RS-232C board doesn't show RAM chips, only the standard serial chips 8251 and 8253 and some logic chips. You can't see at all how it is connected to the I/O ports.

By RetroTechie

Paragon (1563)

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08-09-2012, 21:37

Sure, hit me with that 15MB. LOL!

Manuel wrote:

(..) only the standard serial chips 8251 and 8253

Well that's the most important info right there. I should have datasheets for those, pretty common types for RS-232 and MIDI interfaces.

By msxholder

Champion (399)

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08-09-2012, 21:44

Right now it's getting some interesting details.
HX20 HX21 msx1
HX23 HX34 msx2
All four pieces can be installed with the same extra print RS 232
You can borrow it from the HX22gb or hx22 jap.
So how is lay out of the slots and memory
Try call memini on msx 1 from toshiba
still two toshiba missing HX30 and HX32

By Manuel

Ascended (19270)

Manuel's picture

08-09-2012, 22:33

RetroTechie: the datasheets don't help, they don't say how they're connected to the I/O ports...

By RetroTechie

Paragon (1563)

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09-09-2012, 03:18

I've been reading a bit through RS-232 sections in MSX Technical Databook (page 20-23) and Sony G900 service manual (page 42) and those implementations seem a) compatible, and b) a quick glance at the HX-22 RS-232 ROM appears it uses I/O addresses in that range as well.

So there seems to be some sort of standard (8251 on I/O ports 80/81h, 8253 on I/O ports 84-87h). With some bits on I/O port 82h defined, some not.

Those bits have to get onto the databus somehow, and looking at the photos you sent me, I'd say the 74LS367 (IC3) on the RS-232 board is the IC that does that. So you'd have to check connections for that IC. Chances are Z80 D3 line connects to one of its pins, then you'd have to trace back where the corresponding input of that LS367 is wired to.

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