Add a reset button to the FS-A1

Door gdx

Enlighted (4637)

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20-01-2021, 08:21

Here is a small diagram to show how to add a soft reset button on the Panasonic FS-A1 computer. This is possible on the FS-A1 because it uses an MSX-System II chip without buffer and reset signal is directly connected to the Z80 and VDP.

Connected this way, pressing the button causes just a soft reset. The contents of the RAM will not be cleared so it will still sometimes be necessary to shut down the MSX.
However, the problem can probably be solved by adding in the internal ROM a routineat the start of initialization that clears just the first RAM found of the pages 1-3 (4000h-FFFDh) in slots. I have not tried yet.

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Van Daemos

Paragon (1951)

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20-01-2021, 13:35

Love the idea. I learned there exist msx computers without a reset button and i was just wondering. What if you add a relais to the +5v supply line and that relais opens upon pressing the "reset" button. Its not a real reset but it sure resets the msx. Basicly a on off switch that turns the computer off when you press it but turns it on when you release it. It should do the job.

Van gdx

Enlighted (4637)

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21-01-2021, 08:54

The button can be placed in the back right corner like the picture below if it is sufficiently small. There is just a hole to be drilled with a button of this type.

@Daemos
Capacitors can cause problem with a relay if you doesn't press for a while and it takes up space. It creates also a magnetic field and interference.

Van Daemos

Paragon (1951)

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21-01-2021, 13:48

Space is indeed a problem. Magnetic interference should be minimal if you feed the relais dc. However the capacitors should indeed be a big problem. Forgot about the smoothing caps. Two channel relais with small resistance to ground should discharge the caps. Takes up even more space. Doable but not without problems.

Van sunn

Resident (58)

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28-01-2021, 13:05

Really nice progress. Maybe RF connector could be removed instead? I doubt many people will benefit from the Japanese RF and no drilling needed.

Van sunn

Resident (58)

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28-01-2021, 13:08

Other projects that would be interesting:
-Internal RAM expansion
-Adding FM Music ROM
-MSX 2+ mod?

Van gdx

Enlighted (4637)

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28-01-2021, 14:41

In the wiki, there are links to make it but in Japanese.

gdx wrote:

The button can be placed in the back right corner like the picture below if it is sufficiently small. There is just a hole to be drilled with a button of this type.

You need a push button of 8mm to make it.

Van Fabf

Champion (258)

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29-01-2021, 08:13

Hi gdx
You can download and print my cartridge cover here : https://www.thingiverse.com/thing:4653277

Van gdx

Enlighted (4637)

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29-01-2021, 10:27

Thank you, I had taken the measures so that someone could do it but you got ahead of me. Smile