What is the function of the digital input when set as a door switch?

When configured as a door switch ('IF=do'), the relay output and compressor status can be controlled with parameters 'dC': no = normal, Fn = fans off, cP = compressor off, Fc = both compressor and fans off. A delay before enabling the open-door alarm is set with ‘di’. The regulation restarts if 'rd' = y after the delay. (Page 2)