ADRHEXADRNAMEDescriptionshadowOS
621$026DKEYDISKeyboard disablenoneX

POKE with 255 to disable the keyboard, 0 to reenable. You have to press RESET (all XL/XEs except 1200XL) to get control back if you are locked out; 1200XL users can press CTRL-F1 (toggles it on and off; LED 1 is on when the keyboard is disabled).