The Holtek HT66F018 is a Flash microcontroller designed with an OTP (One Time Programmable) feature. It is housed in a 20-pin SSOP-150mil RoHS package. This device is primarily designed to be used as an OTP programmer, by allowing a user to program it with their desired program or data. The device has a built-in 8-bit CPU core, a 16-bit data bus, a 6-level interrupt hierarchy, and an E2 memory. It also provides peripheral functions such as a 10-bit Analog-to-Digital Converter (ADC), UART, and an I2C/SPI interface. The HT66F018 also has a low-voltage operation mode, which allows it to operate at just 1.5V. The device is manufactured by Holtek, a leading provider of core functionality and system solutions for a wide range of consumer, automotive, and industrial applications.