The DCO is used for the M Clock and high-frequency clocks. The LFXT1 can also be used in a high-speed mode with a 1:8 megahertz crystal connected to it. The set up and control for the DCO in the 1xx basic clock system is shown here. Below this, two registers are shown that contain three bit fields – the RSEL bit field, the DCO bit field and the MOD bit fields. Each of these three bit fields has a specific control function for the DCO. The RSEL bit fields control or select a general range that the DSO operates in while the DCO bit field subdivides that range by 8. This combination of the RSEL and the DCO bit fields provides 64 discrete frequencies for the DCO to operate at. The MOD bits provide a way to effectively divide each DCO range again by 32. The way this is done is by a modulator inside of the DCO that mixes two adjacent DCO frequencies according to the MOD bit settings. The result is a synthesized or an effective clock frequency of the desired value.