The MSM64P164 is a one-time-programmable ROM-version product, which has one-time PROM (OTP) as internal program memory. On the other hand, the MSM64164C is a mask ROMversion product, which has mask ROM as internal program memory. Unlike the mask ROM-version MSM64164C, which has a P-well CMOS structure, the MSM64P164 has been fabricated with the N-well CMOS-structured EEPROM process technology. Therefore, the MSM64P164 differs from the MSM64164C in the polarity of the power supply for LCD bias generation and 5 V interface, and in the external circuit structure. Unlike the mask ROM-version product, the MSM64P164 cannot be supplied in the form of a chip. The MSM64P164 is an OTP-version product used to evaluate an application program. The MSM64P164 has two operation modes, microcontroller operation mode and PROM mode. The microcontroller operation mode is used to operate the MSM64P164 like a mask ROM-version product and the PROM mode is used to program or read the PROM.