Chapter6: Memory unit

Asst.Prof.Dr.Supakit Nootyaskool Objective

• To learn structure inside of memory

• To understand difference between static memory and dynamic memory

• To explain why the memory having address , bus, and control signal. Memory types

Semiconductor Memory

Types volatile Non-volatile

ROM, EPROM, NVRAM, Flash Static RAM Dynamic Ram Technologies EEPROM memory Memory types

Semiconductor Memory

Types volatile Non-volatile

ROM, EPROM, NVRAM, Flash Static RAM Dynamic Ram Technologies EEPROM memory No need a power supply to preserve the Need a power supply to data preserve the data • More expensive • High speed (highMemory access types time) • At the same package Semiconductorsize, SRAM has low Memory capacity

Types volatile • CheaperNon-volatile • Low speed (long access time) ROM, EPROM, NVRAM, Flash Static RAM Dynamic Ram • Technologies EEPROMAt the samememory package size, DRAM has high capacity. Static RAM (SRAM)

• SRAM created from D flip-flop.

D Clk Q 0 0 1 1 SRAM and DRAM in Video GAME

8- CPU

Picture processing Unit Character representation in ASCII code “A” 41H = 01000001 Static RAM keeps “A” 0 1 0 0 0 41 = 01000001 0 0 1 Static RAM keeps “A” 0 0 1 1 0 0 0 0 0 0 41 = 01000001 0 0 0 0 1 1 Static RAM

1 . . Memory Size 2 . . 8 x 1024 = 8192 ≈ 8K . . 3 . . 4 . . . . 5 . . . . 6 . . 7 . .

8 . .

1 2 3 ……. 1024 • Data • 8Bit SRAM • D0-D7 1 . . 2 . . . . 3 . . 4 . . . . 5 . . • Address . . • 1024 Address = 2^? 6 • 1 2 4 8 16 32 64 128 256 . . 512 = 10Lines (A0-A9) 7 . .

8 . .

1 2 3 ……. 1024 Static RAM

A memory chip has 3 group of pins

Latch 1) Data bus is bi-directional 2) Address bus is input

D0-D7 8

bit 3) Control signals are read, write, chip enable, R/W

Decoder

10:1024

A9

- A0 Concept of Dynamic RAM

Refresh circuit Charge/Discharge Capacitor DRAM

Refresh circuit

DRAM Latch

D0-D7

8 bit

R/W

Refresh Decoder

10:1024

A9

- A0 Comparing structure of memory devices in 1 bit

Dynamic RAM Static RAM Other types

• Speed access improvement – EDO DRAM (Extended data-out DRAM) – SDRAM (Synchronous DRAM) – DDR SDRAM ( SDRAM) – RDRAM ( DRAM) • More than a data bus – VRAM (Video RAM) – SGRAM (Synchronous graphic ram) ROM

• PROM (Programmable read only memory) Read Only Memory (ROM)

• EPROM (Erasable PROM)

UV ROM

• Electrical EPROM (Erasable PROM)