Re: Commodore joystick ports

From: Jim Brain (
Date: 2007-05-09 08:56:20

Daniel O'Shea wrote:
> I was wondering, in both Jim and Levente's microcontroller to joystick 
> port projects - is interfacing a microcontroller's digital output 
> (high/low) to the joystick input likely to cause the same issues with 
> the CIA chip as noted here:
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I doubt either of our projects has this issue.  In mine, for example, IO 
is done thusly:

output to joy      DDR         logic level         notes
HI                        input         high                  internal 
pullup engaged
LO                       output      lo                      tied 
directly to ground (well, close to it)

LO->HI:   switch DDR to input, then switch logic level to high to engage 
pullup.  Doing it this way ensures you never drive pin with 5v directly
HI->LO:   disengage pullup, then switch DDR to output.


Jim Brain, Brain Innovations                                      (X) 
Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times! 

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