Unlike conventional Flash memories that are accessed randomly, these two SPI NOR
access data sequentially. They operate from a single 2.7-3.6 V power supply for program
and read operations. They are enabled through a chip select pin and accessed through a
three-wire interface: Serial Input, Serial Output, and Serial Clock.
28.1.2 Software Operation
In a Flash-based embedded Linux system, a number of Linux technologies work together
to implement a file system. Figure below illustrates the relationships between some of the
standard components.
Figure 28-1. Components of a Flash-Based File System
The MTD subsystem for Linux is a generic interface to memory devices, such as Flash
and RAM, providing simple read, write, and erase access to physical memory devices.
Devices called mtdblock devices can be mounted by JFFS, JFFS2 and CRAMFS file
systems. The SPI NOR MTD driver is based on the MTD data Flash driver in the kernel
by adding SPI access. In the initialization phase, the SPI NOR MTD driver detects a data
Flash by reading the JEDEC ID. Then the driver adds the MTD device. The SPI NOR
MTD driver also provides the interfaces to read, write, and erase NOR Flash.
28.1.3 Driver Features
This NOR MTD implementation supports the following features:
• Provides necessary information for the upper layer MTD driver
Introduction
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