C64 Keyboard Scanning

From: COPLIN, Nicholas. (ncoplin_at_orbeng.com.au)
Date: 2000-10-10 09:28:11

Hi All,

how does the C64 kernal scan the keys - does it strobe column by column (pa0
- pa7, one by one) and read the answer in pb0 - pb7; or does it set all
columns at once?

I'm wanting to drive something off the Joystick ports (eg a rumble-pack type
device), but I want it only to respond to specific codes, not the keyscan
routines.  I'm hoping that I can use illegal joystick moves as a code (ie
grounding left and right at the same time), but this won't work if the
keyboard routine also grounds more than one line at a time.

Does anyone know the answer?

- Nick


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