Memory: World of Binary Code

Abstract

Transistor is indispensable circuit element for electronic device. In present, the number of transistors integrated in integrated circuit (IC) has become double every 1.5–2 years, following Moore’s law. Microcontroller unit consists of central processing unit (CPU), main memory, input and output. In present main memory, data is temporarily stored in volatile memories such as Dynamic Random Access Memory (DRAM) and Static Random Access Memory (SRAM). In memory, binary number system is applied in order to express character and decimal number. Hence, two different states are recognised as 0/1 digital information. Volatility implies that digital data disappears, when stopping supply of electric energy. DRAM and SRAM are volatile. For data storage memory, floating gate memory such as Electrically Erasable Programmable Read-Only Memory (EEPROM) and Hard Disk Drive (HDD) are in practical use. Recently, Solid State Drive (SSD) is getting popular rather than HDD for personal computers. EEPROM, HDD and SDD are classified as non-volatile memory. In recent years, non-volatile memory for main memory has been actively developed for further high performance computing. The candidates include Ferroelectric Random Access Memory (FeRAM), Ferroelectric-gate Field Effect Transistor (FeFET), Magnetoresistive Random Access Memory (MRAM), Resistive Random Access Memory (ReRAM) and Phase Change Memory (PCM). Each non-volatile memory has unique operating mechanism. It is phenomenologically explained how to read and write 0/1 digital information.