The Digital tab contains a series of predefined diagnostic values for the "Slave diagnostics" module:

Slave is in exchange mode

Shows that a slave is in exchange mode, thus sends and receives Data Exchange Telegrams. This is the normal state.

Currently active bus (for redundant slaves)

If redundancy mode is activated, the bus currently active for the diagnosed slave is displayed here (0: bus 0, 1: bus 1). For further information on the redundancy mode, see chapter Redundancy mode.