UM0851 Datasheet, PDF (143/245 Pages) STMicroelectronics – SPEAr is a family of highly customizable ARM-based embedded

UM0851
Non-volatile memory device drivers
1. If you want to change the partition size, the emi_norflash_partitions table should be
modified.
2. 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.
3. Set emi_norflash_resource.end as NOR_FLASH_PHYS + < Flash size > - 1
5.3
5.3.1
Serial NOR Flash driver
The serial NOR Flash is the primary method for booting the system. This section describes
the controller driver.
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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