The PD75516 is a product in the 75X series(of 4-bit single-chip microcomputers). The 75X series has an architecture which is comparable to that of 8-bit microcomputers. The PD75516 possesses high class processing capacities as a 4-bit single-chip microcomputer with built-in A/D converter and serial interface, including the capability to process data in lengths of 1, 4 and 8 bits in addition to its high speed operation.