Re: Commodore 65 and DIN8 cable

From: Michał Pleban <>
Date: Thu, 03 Mar 2016 21:34:06 +0100
Message-ID: <>
Michał Pleban wrote:

> This is the DISK_RD signal without any cable:
> Here it is with 30cm cable attached:
> As you can see, the rising edge of the signal trails off a bit longer.
> This is even more visible with a 1m cable:
> Here it is really bad. I understand that the signal rises more slowly,
> thus the decoder sees logical "0" longer than it should and throws errors.

Problem solved. I was thinking on it and the signal looks pretty much
like an RC delay. As if the drive was pulling the data line high with a
resistor, but the cable introduced some capacitance.

So I decided to pull the line up with 150 Ohm and voila, the signal

Not enough for the chip to read without errors, so I added another
resistor in parallel making it 75 Ohm, and it's even better:

Now the drive reads everything fine with a 1m cable! For 3m cables, I
guess I would need 30 Ohm or something.

So in the end, it was really termination. I was just using too high
resistors when I tried that in the beginning...


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Received on 2016-03-03 21:00:12

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