The PD7564A is a 4-bit single-chip microcomputer with a small number of ports in a small package, which is of low-order models, PD7554 and 7564 sub-series in the PD7500 series. With an on-chip serial interface, it performs efficient dispersion processing of a system as a sub-CPU for the 75X series or 78k series. The PD7564A has outputs to directly drive a triac and LEDs and allows selection among many types of input/ output circuits using their respective mask options, sharply reducing the number of external circuits required. Details of functions are described in the User's Manual shown below. Be sure to read in design. PD7554, 7564 User's Manual: IEM-1111D