I'm trying to implement the CiA 401(I/O). But I don't know how the device should behave if the object 6002 (input polarity) changes. Should the value in object 6000 (read input) also change and if so, a PDO should also be sent, although nothing has changed at the physical input?
The only mandatory input polarity objects are 6002:0 and 6002:1, and it should affect the polarity of the corresponding digital on/off objects objects mapped at 6000. Note that DS-401 lists an "Entry Category" which dictates which objects and indices that are mandatory and which that are optional.
If you map the input polarity, it will be a RPDO in your application, and affect whatever TPDO that 6002 is mapped into. As far as I remember, the values inside 6000 should not change, only the values of the relevant TPDO. This TPDO will only be sent when it should - that is, depending on how it is configured: cyclic, on change, on request etc.