The 4554 Group is a 4-bit single-chip microcomputer designed with CMOS technology. Its CPU is that of the 4500 series using a simple, high-speed instruction set. The computer is equipped with main clock selection function, four 8-bit timers (each timer has one or two reload registers), interrupts, and LCD control circuit. The various microcomputers in the 4554 Group include variations of the built-in memory size as shown in the table below.