Overview

Objective: The study of memories was initiated in Chapter 16, where volatile types were described, and it concludes in this chapter, where nonvolatile memories are presented. The following nonvolatile types are included below: MP-ROM, OTP-ROM, EPROM, EEPROM, and flash memory. A special section on promising next-generation nonvolatile memories is also included, where FRAM, MRAM, and PRAM memories are described.

Chapter Contents

17.1 Memory Types

As mentioned in Section 16.1, nearly all modern digital designs require memory, which can be divided into volatile and nonvolatile. The former type was seen in Chapter 16, while the latter is studied here. The complete list is shown below, where some promising next-generation technologies are also included.

Volatile memories (Chapter 16):

• SRAM (static RAM)

• DDR and QDR (dual and quad data rate) SRAM

• DRAM (dynamic RAM)

• SDRAM (synchronous DRAM)

• DDR/DDR2/DDR3 SDRAM (dual data rate SDRAM)

• CAM (content-addressable memory) for cache memories

Nonvolatile memories (Chapter 17):

• MP-ROM (mask-programmed ROM)

• OTP-ROM (one-time-programmable ROM, also called PROM)

• EPROM (electrically programmable ROM)

• EEPROM (electrically erasable programmable ROM)

• Flash (also called flash EEPROM)

Next generation memories (Chapter 17):

• FRAM (ferroelectric RAM)

• MRAM (magnetoresistive RAM)

• PRAM (phase-change RAM)

17.2 Mask-Programmed ROM (MP-ROM)

The first type of nonvolatile memory to be described is MP-ROM (mask-programmed read only memory), which is programmed during fabrication.