Gianmario.Scotti_at_nokia.com
Date: 2003-06-18 01:31:43
¤-----Original Message-----
¤From: ext David Wood [mailto:jbevren@starbase.globalpc.net]
¤Sent: 17 June 2003 17:41
¤To: cbm-hackers@cling.gu.se
¤Subject: Re: C-64 joystick port, pin 7
¤
¤
¤But you CAN draw so much that the system becomes mysteriously
¤unstable ;-)
Absolutely. In fact, the circuitry in the 7805 has an overcurrent/short protection called "fold-back", if I remember correctly. That will not just limit the current, the circuitry will actually decrease the current as the load increases. When fold-back current overload protection kicks in, it overrides the negative feedback loop inside the 7805 - output voltage falls like a rock. (btw. I found this quote from an LM 78xx datasheet: "Each type employs internal current limiting,
thermal shut-down and safe area protection, making it essentially indestructible.")
But I think I ought to inform you why did my C-64 not reset when I pressed the Fire button on the Amstrad joystick (and notice I didn't say Fire 1 or Fire 2): it appears that this particular Amstrad joystick was made compatible to the C-64, so pin 7 is not connected at all, while both Fire buttons are wired to pin 6.
So, we still don't know what would happen if pins 7 and 8 where shorted. If someone's curous, please do try. There is all reason to believe that no permanent damage will be caused to your C-64 (tongue-in-cheek).
cheers
mario
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