The GMS81C2020 and GMS81C2120 are an advanced CMOS 8-bit microcontroller with 20K/12K bytes of ROM. These are a powerful microcontroller which provides a highly flexible and cost effective solution to many VFD applications. These provide the following standard features: 20K/12K bytes of ROM, 448 bytes of RAM, 8-bit timer/counter, 8-bit A/D converter, 10-bit High Speed PWM Output, Programmable Buzzer Driving Port, 8-bit Basic Interval Timer, 7-bit Watch dog Timer, 8-bit, Serial Peripheral Interface, on-chip oscillator and clock circuitry. They also come with high voltage I/O pins that can directly drive a VFD(Vacuum Fluorescent Display). In addition, the GMS81C2020 and GMS81C2120 support power saving modes to reduce power consumption. This document is only explained for the base of GMS81C2020(GMS81C2120), the eliminated functions are same as below. Device name