They both have one: https://archive.org/details/commodore-64-manual-en-1982/page/142/mode/2up https://archive.org/details/commodore-64-manual-en-1982/page... O

They both have one: https://archive.org/details/commodore-64-manual-en-1982/page/142/mode/2up https://archive.org/details/commodore-64-manual-en-1982/page... On the user port I managed to short 5V to GND instead :'(