26.3.6 Debug Operation
During run-time debugging, the TWI will continue normal operation. Halting the CPU in
      Debugging mode will halt the normal operation of the TWI. The TWI can be forced to operate
      with a halted CPU by writing a ‘1’ to the Debug Run (DBGRUN) bit in the Debug
      Control (TWIn.DBGCTRL) register. When the CPU is halted in Debug mode, and the DBGRUN bit is
        ‘1’, reading or writing the Host Data (TWIn.MDATA) register or the Client
      Data (TWIn.SDATA) register will neither trigger a bus operation nor cause transmit and clear
      flags. If the TWI is configured to require periodical service by the CPU through interrupts or
      similar, improper operation or data loss may result during halted debugging.
