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Advantages of surface-mount SSDs

Posted: 13 May 2013 ?? ?Print Version ?Bookmark and Share

Keywords:NOR flash. NAND device? solid state drive?

For operating systems where the support is not intrinsic, a similar process needs to be created for the specific OS. The basic principles are outlined below

Specific header files will need to be included that handle the modified global variables for the drivers (MCU_sys.h). Consider the NANDrive managed NAND flash memory device as an example. ATA register definitions would be included in the ata.h header as well as NANDrive specific definitions and variables, which would be included in NANDrive.h. Examples of MCU_sys.h, ata.h and NANDrive.h are available from Greenliant Systems.

Specific implementation of the NANDrive registers and data area would be handled by the NANDrive.c file, which should be modified depending on the type of MPU/MCU that is employed.

The example NANDrive generic driver provides the following functions to the system software:

???inti_NANDrive(): Function is used to initialise task file register addresses and read NANDrive parameter information.
???reset_NANDrive(): Function is used to let NANDrive perform software the reset operation
???check_error(): Function returns the error code which is defined in NANDrive.h
???check_status(): Function returns the status which is defined in NANDrive.h
???read_n_sectors(): Function is used to read up to 64 sectors data out from NANDrive
???write_n_sectors(): Function is used to write up to 64 sectors data into NANDrive
???tmr_chk_timeout(): Function is used to check if function is returned in time
The sample NANDrive driver offers two ways to access data residing in the surface-mount SSD data sectors:

???Data polling mode: After the host issues an ATA command, the MCU/MPU keeps polling the status register to decide when to start a data transfer.
???Interrupt mode: MCU/MPU can return to some other operation after issuing an ATA command to the drive. An interrupt to the MCU/MPU will be triggered when the device is ready for data transfer. Using this mode can allow the MCU to save time with other operations.

The code snippet below shows an example of using the NANDrive.c driver:

The advent of managed NAND devices in a small form factor, BGA package allows embedded systems designers to adopt a PC-style architecture when designing new systems. The approach allows them to capitalise on surface-mount SSD advantages like easy integration and expanded functionality to develop prompt and cost effective designs. With no additional IDE control hardware required, a PATA-compliant managed NAND flash memory device can easily be connected to a microcontroller on the memory bus. Compared to expensive high-density NOR, surface-mount SSDs offer a compelling choice for code and data storage in embedded systems.

About the author
Ralph Thomson is director of field applications engineering at Greenliant Systems, manufacturer of NANDrive embedded solid state drives, NAND flash memory controllers and other high-reliability solid state storage products. He has more than 25 years of experience in applications engineering and product management working with all aspects of electronics, from OEM/ODM design to product definition and chipset support. He holds a BSc with Honours in physics with microelectronics from the University of Wales, Swansea.

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