Vhd interface for victor hc90/95

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Par sdsnatcher73

Prophet (3666)

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31-05-2022, 20:23

It is of course possible they managed to combine the 2 functions. I mean before they apparently had 2 microprocessors on the board to do separate functions. In a cost reduction effort they may have found a way to execute both functions on just 1 microprocessor.

But to really know we must find out what the functions are and if they are indeed present in both revisions (of course easier said than done). Also it is of course weird that the C revision has the extra processor but not the extra terminal whilst the D lacks the processor but has the extra terminal.

Par gdx

Enlighted (5842)

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01-06-2022, 09:54

I's possible that the NEC D24C2000C-X02 is not a Kanji-ROM as supposed on japanese sites but an equivalent of the D80C49C. I can't found specifications but it seems to me less and less likely that it is a Kanji-ROM.

Par mars2000you

Enlighted (6346)

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01-06-2022, 10:25

gdx wrote:

I's possible that the NEC D24C2000C-X02 is not a Kanji-ROM as supposed on japanese sites but an equivalent of the D80C49C. I can't found specifications but it seems to me less and less likely that it is a Kanji-ROM.

So this device could use the RAM inside this chip + the internal memory mapper as RAM disk?

It could be possible ... we still need to find the MK1 (probably without RAM disk feature).

Par popolon_

Champion (297)

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02-06-2022, 19:00

Apparently that 80C49C contains rom, and that could be read as somebody has done that for same kind
https://qemulator.blogspot.com/2020/05/dumping-intel-8049-ro...
But then i would have to desolder the chip, or isolate it from pcb circuit. Maybe risky thing to do. Anyway i try to draw schematics for this pcb tomorrow.

Par popolon_

Champion (297)

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03-06-2022, 21:02

It seems vhd connector pins 3,4,6,7,8,9,10,12 are used in this both versions. In this stripped down version 3,4,8,10,12 are really connected to logic and pin 7 just pulled up to +5v. In fully populated pcb, also the pins 6,7,9 are connected to logic (4069 ic).
In both versions Pin 14/15 is connected to ground.
Vhd pins 8,10,12 goes to 80C49C 36,37,38 pins
8 -> 36
10 -> 37
12 -> 38

Par popolon_

Champion (297)

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04-06-2022, 16:13

Here is initial schematics (not drawn those unpopulated ic connections, except towards that second 80C49C).
The signal label names are for that 96 pin connector where there are three rows (A1-32,B1-32,C1-32), so not the actual signal names.
vhd_card_schematics82513f850d3a3039.png
i put current drawing into: https://github.com/popolonx/MSX_STUFF/tree/main/vhd_c9d_card

Par popolon_

Champion (297)

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04-06-2022, 19:02

I added real signal names to schematics and few errors corrected.
vhd_card_schematics_newer.png

Par popolon_

Champion (297)

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05-06-2022, 08:22

And now some hoarder is preventing me from getting Thunder msx cassette for dump. It is almoust like somebody is just buying stuff to prevent others from dumping the content. I hate these selfish collectors.

Par popolon_

Champion (297)

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05-06-2022, 12:25

I looked at inside victor hd 7900 vhd player to where the signals are going. DIN-13 pins 3,4,8,11,12 are going inside same internal connector and towards 8050 type rom mask cpu. Pins 7,9,10,13 are going to aomewhere else. Pin 5 is ground. Pin 6 goes via 1k resistor to internal connector that has also analog video/audio output signals. Pin 1 and 2 goes to some other place.

Par popolon_

Champion (297)

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05-06-2022, 17:18

I won that thunder msx vhd cassette, so hopefully the cassette can be read correctly and no magnetic field has wiped out the data( still pissed of that the national frame unit software disk was wiped out completely).

Now i looked at what Sharp X1 vhd software cassette i have.
Google translation shows Vhd language interpreter:
IMG_20220605_163215192.jpg
IMG_20220605_163203540.jpg
So this cassette is needed in Sharp X1 to play those few games that have game data on vhd disk itself. So some hardcore coder could port this to MSX?

Anyway back to vhd player, following din13 pins are output from player
-pin 2, from mb88401 cpu pin36, through transistor.
-pin 1 ground for pin 2, pin 5 ground is not same.
-pin 6, analog audio or video from mitsubishi m51688p ic pin19
-pin 7, ttl level logic signal from fujitsu mb54893p ic pin14 via hex buffer.
-pin 9, ttl level sync signal or what? from mitsubishi m51688p ic pin23 via hex buffer.
-pin 10, ttl level logic signal from fujitsu mb54893p ic pin17 via hex buffer.
-pin 11, ttl level logic from 8050H cpu pin36 ( P25) via hex inverter.

Input pins
-pin 8, to 8050H pin39 (timer/counter input)
-pin 12, pulled up to +5v via 3k2 resistor, goes to ba222 timer ic, pin 5(trigger)

Input/output?
-pin 4, goes to NPN transistor C1740 collector. Emitter goes to 88401 cpu pin 31 (output pin). Base comes from 8050H cpu pin 21(P12, quasi bidirectional port).

Not used pins
-pin 3 (only diodes from ground and towards +5v)
-pin 13, it is pulled up to +5v via 4k7 resistor.

Pins 3,4,7,8,9,10,11,12,13 have diodes from ground and towards +5v.

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