The GMS87C1102 and GMS87C1202 are an advanced CMOS 8-bit microcontroller with 2K bytes of ROM. The HYUNDAI MicroElectronics GMS87C1102 and GMS87C1202 are a powerful microcontroller which provides a highly flexible and cost effective solution to many small applications. The GMS87C1102 and GMS87C1202 provide the following standard features: 2K bytes of ROM(OTP), 128 bytes of RAM, 8-bit timer/counter, 8-bit A/D converter, 10-bit High Speed PWM Output, Programmable Buzzer Driving Port (GMS87C1202 only), on-chip oscillator and clock circuitry. In addition, the GMS87C1102 and GMS87C1202 support power saving modes to reduce power consumption. This document is only explained for the base of GMS87C1202, the eliminated functions are same as below.