Avoid conflicts between C64 keyboard and joystick #1

The Commodore 64 keyboard may display unexpected characters when joystick #1 is used. There is a solution! Avoid the keyboard when scanning the joystick, and exclude the joystick data when scanning the keyboard. But somewhat easier said than done. Tracing the source of the issue is that PORTB of CIA1 is connected to the keyboard and first joystick simultaneously. Normally the C64 KERNAL IRQ will…