Sets the internal clock frequency for the Graychips on DTDM/DTDMX modules. This defaults to 101MHz to handle oversampling up to 100MHz. In some applications this can be increased to handle rates up to 110MHz if adequate cooling is supplied. TCLK=n is specified in Hz. For example config: ICEPIC,DEVNO=0,TCLK=110000000,IOM=A2D,...