Jazan University, Jazan KSA Chapter 5 Lecture 11 Faheem Lecturer, CNET Dept., Jazan University, Jazan KSA Internal Memory

Topics in this chapter Semi Conductor Main Memory. Dynamic Random Access Memory [DRAM]. Static Random Access Memory [SRAM] and Read Only Memory [ROM]

Semiconductor Main Memory In old computers, the most common form of random-access memory was an array of ferromagnetic material referred as cores. Hence, main memory was also called as core. Today due to development of microelectronics magnetic core memory is vanished, and the use of semiconductor chips for main memory is universal for all computers. Book Page No 159

Main Memory Organization The basic element of a semiconductor memory is the memory cell, all semiconductor memory cells share certain properties: They exhibit two stable (or semi-stable) states, which can be used to represent binary 1 and 0. They are capable to write into, to set the state. They are capable of being read to sense the state. Book Page No 160

Set and sense state

Main Memory Cell The cell has three functional terminals for carrying an electrical signal. The select terminal, selects a memory cell for a read or write operation. The control terminal indicates read or write. For writing, data terminal provides an electrical signal that sets the state of the cell to 1 or 0. For reading, this terminal is used for output of the cell’s state, Book Page No 160

Semiconductor Memory Types The table shows all Semiconductor Memory Types The most common is Random Access Memory. Book Page No 160

Random Access Memory [RAM] The memory is accessed in random manner that’s why it is called as random access memory. It is Read/Write memory It is Volatile memory It is a Temporary storage Its of two type Static or dynamic.

Dynamic RAM Bits stored as charge in capacitors Charges leak Need refreshing even when powered Simpler construction Smaller per bit Less expensive Need refresh circuits Slower Main memory Analogue Book Page No 160-161

Dynamic RAM Structure Book Page No 160-161

DRAM Operation Write Address line active when bit read or written Transistor switch closed (current flows) Write Voltage to bit line High for 1 low for 0 Then signal address line Transfers charge to capacitor. Book Page No 160-161

DRAM Operation Read Read Address line selected transistor turns on Charge from capacitor fed via bit line to sense amplifier Compares with reference value to determine 0 or 1 Capacitor charge must be restored Book Page No 160-161

Thank you!!!

On 20th of April 2016 Wednesday [12 to 01] On Chapter 3 and 4. Exam 2 On 20th of April 2016 Wednesday [12 to 01] On Chapter 3 and 4.