Flash controller

A flash memory controller (or flash controller) manages the data stored on flash memory and communicates with a computer or electronic device. Flash memory controllers can be designed for operating in low duty-cycle environments like SD cards, CompactFlash cards, or other similar media for use in digital cameras, PDAs, mobile phones, etc. USB flash drives use flash memory controllers designed to communicate with personal computers through the USB port at a low duty-cycle. Flash controllers can also be designed for higher duty-cycle environments like solid-state drives (SSD) used as data storage for laptop computer systems clear up to mission-critical enterprise storage arrays.

After a flash storage device is initially manufactured, the flash controller is first used to format the flash memory. This ensures the device is operating properly, it maps out bad flash memory cells, and it allocates spare cells to be substituted for future failed cells. Some part of the spare cells is also used to hold the firmware which operates the controller and other special features for a particular storage device. A directory structure is created to allow the controller to convert requests for logical sectors into the physical locations on the actual flash memory chips.

When the system or device needs to read data from or write data to the flash memory, it will communicate with the flash memory controller. Simpler devices like SD cards and USB flash drives typically have a small number of flash memory die connected simultaneously. Operations are limited to the speed of the individual flash memory die. In contrast, a high-performance solid-state drive will have as many as 100 or more dies organized in a matrix with parallel communication paths to enable speeds many times greater than that of a single flash die.

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