For allowing a port to serve as not only one of the system clock input port but also a data input/output port, there is disclosed a data processing unit comprising a system clock supplying circuit operative in an internal oscillation mode or a transmission mode depending upon a mode selecting signal,...http://www.google.fr/patents/US4910703?utm_source=gb-gplus-shareBrevet US4910703 - Data processing unit having multiple-purpose port used as a resonator connection port in first mode and as a data i/o port in second mode
Data processing unit having multiple-purpose port used as a resonator ...
