Memory (RAM, ROM, EEPROM)

Random Access Memory (RAM)

RAM is a type of volatile memory that can be both read from and written to, where “volatile” means the data stored is lost when power is removed.
RAM is used by microprocessors and microcontrollers to temporarily store and manipulate data while an embedded system is operational.
Two main types of RAM are Static RAM (SRAM) and Dynamic RAM (DRAM). SRAM retains stored information as long as power is supplied, but DRAM needs to be refreshed periodically.
Compared to other types of memory, RAM has a faster access speed, but is more expensive and consumes more power.

Read Only Memory (ROM)

ROM is a non-volatile memory where data is written during the manufacturing process and cannot be modified or erased by normal computer operations.
ROM is primarily used to store the boot code and other permanently needed programs in embedded systems.
Types of ROM include Masked ROM, Programmable ROM (PROM), and Erasable Programmable ROM (EPROM), each with unique capabilities and usage scenarios.

Electrically Erasable Programmable Read-Only Memory (EEPROM)

EEPROM is a type of non-volatile memory that can be electrically programmed and erased multiple times without removing it from the system.
Unlike RAM, data stored in EEPROM is not lost when power is removed, making it a reliable storage method for long-term use.
EEPROM is typically used in embedded systems to store system parameters or setup information that can change over time, and needs to be preserved between power cycles.
Although slower and less durable than RAM, EEPROM is valuable for its persistence and flexibility in an embedded system design.

Usage in Embedded Systems

Choice of memory type in an embedded system design depends on the specific requirements of the system, including speed, power consumption, data retention needs, and costs.
Most embedded systems use a combination of these memory types to achieve a balance between performance and power efficiency.