DESCRIPTION
The 4551 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 an 8-bit timer with a reload register, a 14-bit timer which is also used as a watchdog timer, a 4-bit timer with a reload register, a carrier wave output circuit and an LCD control circuit.
The mask ROM version and built-in PROM version of 4551 Group are produced as shown in the table below.

FEATURES
● Minimum instruction execution time ............................ 1.5 µs
   (f(XIN)=8.0 MHz, VDD=5.0 V, system clock = f(XIN)/4)
● Supply voltage
   ............................. 2.5 V to 5.5 V (One Time PROM version)
   ....................................... 2.2 V to 5.5 V (Mask ROM version)
● System clock switch function
   ........................................... Clock divided by 4 or not divided
● LCD control circuit
   Segment output .................................................................. 20
   Common output ....................................................................4
● Carrier wave frequency switch function
   System clock, system clock/2, system clock/8,
   system clock/12, system clock/16, system clock/24, “H” fixed
● Timers
   Timer 1 ................................ 8-bit timer with a reload register
   Timer 2 ...............14-bit timer also used as a watchdog timer
   Timer LC ............................. 4-bit timer with a reload register
● Interrupt ................................................................... 3 sources
● Voltage drop detection circuit ...............................................1
● Clock generating circuit (ceramic resonance and quartz-crystal oscillation)

APPLICATION
   Remote control transmitter