C-64 joystick port, pin 7

Date: 2003-06-16 11:27:07


I got hold, through a purchase of some old junk, of an Amstrad joystick. I boldly proceeded to try it out on my C-64, but noticed something is not quite right. Note that the C-64 didn't reset.

So then I went to check out the Amstrad joystick port pinning, and found out that it uses pin 7 for the Fire 1 button. This deviation from the Atari "standard" is rather alarming, since on the C-64 pin 7 is connected to +5 Vcc. Further analysis of my Commodore showed that the joystick port is still intact and functional. 

How can this be? According to the  C-64 schematic (this part of the schematic should be common to all revisions) http://www.funet.fi/pub/cbm/schematics/computers/c64/250469-rev.A-left.gif pin 7 goes directly to the system's +5 Vcc. So when I pressed the Fire 1 button, I should have fried one of the fuses, or at least reset the system - which didn't happen.

thanks in advance


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