UM0851 datasheet(143/245 Pages) STMICROELECTRONICS

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UM0851

Non-volatile memory device drivers

Doc ID 16604 Rev 2

143/245

If you want to change the partition size, the emi_norflash_partitions table should be

modified.

If the bandwidth of the Flash is 8 bits, set emi_norflash_data.width to 1. If it is 16 bits,

set emi_norflash_data.width to 2. If it is 32 bits, set emi_norflash_data.width to 4.

Set emi_norflash_resource.end as NOR_FLASH_PHYS + < Flash size > - 1

5.3

Serial NOR Flash driver

The serial NOR Flash is the primary method for booting the system. This section describes

the controller driver.

5.3.1

Hardware overview

NOR Flash is a non-volatile memory which is memory mapped and has a standard memory

interface. NOR Flash is well suited to use as code storage because of its reliability, fast read

operations, and random access capabilities. Because code can be directly executed in

place, NOR Flash is ideal for storing firmware, boot code, operating systems, and other data

that changes infrequently. NOR Flash memory has traditionally been used to store relatively

small amounts of executable code for embedded computing devices such as PDAs and cell

phones.

The NOR Flash used in SPEAr platform board is a Serial NOR Flash and is driven by a SMI

(Serial Memory Interface) controller. Serial Memory Interface (SMI), acting as an AHB slave

interface (32-, 16- or 8-bit), manages the clock, data access and status of NOR Flash

memory. The main features of SMI are:

●

Supports a group of SPI-compatible Flash and EEPROM devices.

●

SMI clock signal (SMI_CLK) is generated by SMI using clock provided by the AHB bus;

●

SMI_CLK can be up to 50 MHz in Fast Read mode (or 20 MHz in Normal mode), and it

can be controlled by a programmable 7-bits prescaler allowing then 127 different clock

frequencies.

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