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Whats the deal with controller ports?!


VicViper

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Partly yes. The keyboard and joystick port #1 share some lines of the CIA chip so there could be misreadings of the joystick as keyboard input. Thus many games prefer to use port #2 as it doesn't interfer with anyhthing. Other games managed to get around the misreadings or just didn't care, and were programmed for port #1 instead.

 

Even if Commodore didn't want to reroute the ports, they could easily have gotten away with it by just renaming the ports on the outside so port #1 is closest to the power connector. It might've made more developers use the same port.

 

Actually once you start to PEEK around in the memory map, port #2 is at address 56320 and port #1 is at address 56321 so something went wrong with the labeling on the outside, methinks.

Edited by carlsson
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Actually both ports interfere with the keybord, the way a joystick in port 2 modifies the keyboard readout is just a bit more subtle(*). :)

 

What really puzzles me is that nearly no game could be arsed to simply poll boths ports in single player mode as this is quite easy to do code-wise - yet Uridium is the only game I know that does that.

 

(*) if you scan the keys the way the kernal rom routine does it - custom made scanners may "reverse" the scan direction and thereby also reverse how each joyport interferes with the results.

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Partly yes. The keyboard and joystick port #1 share some lines of the CIA chip so there could be misreadings of the joystick as keyboard input. Thus many games prefer to use port #2 as it doesn't interfer with anyhthing. Other games managed to get around the misreadings or just didn't care, and were programmed for port #1 instead.

 

Even if Commodore didn't want to reroute the ports, they could easily have gotten away with it by just renaming the ports on the outside so port #1 is closest to the power connector. It might've made more developers use the same port.

 

Actually once you start to PEEK around in the memory map, port #2 is at address 56320 and port #1 is at address 56321 so something went wrong with the labeling on the outside, methinks.

Always wondered about that. Also I remember that moving a joystick in port 1 while in BASIC will type in different characters, as if you typed them in using the keyboard.
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