Flash Translation Layers: extending the lifecycle of your devices

Flash Translation Layer

For efficient use of NAND and NOR Flash memory devices in embedded systems a proper flash management is required. A fail-safe Flash translation layer provides a high-performance solution that allows developers to interface to any flash-based media. The flash translation layer presents a simple logical sector interface to an application, such as a file system, and manages the underlying complexity efficiently and safely. Combined with a professional file systems, there is a complete solution for almost any type of media and performance requirement.

    Flash management technologies

    • Enhanced wear leveling
      Due to their technical nature Flash cells have a limited lifetime and can only be erased and programmed a certain number of times before becoming unreliable, i.e. they ‘wear out’. Wear leveling algorithms are used to maximize the life of the chip by moving the data between physical blocks to ensure some cells are not overused relative to others. The implemented algorithms can be fine-tuned to match performance requirements.
    • Error correction codes (ECC)
      Flash manufacturers define the worst-case rate at which wear occurs. Error correction codes are used to ensure the data is always consistent if used within the chip specification. The strength of the required ECC is defined by the worst-case bit failure rate.
    • Bad block management
      Flash memory contains blocks that may be defective when the device is new. Also during operation, data in "good blocks" can be corrupted by charge leakage or disturbance from writes in adjacent parts of the chip.
    • Read disturb errors
      Read disturb errors occur when a read operation on one page causes one or more bits to change in other pages of the same block. Executing many read operations on pages within a block, with no intervening erase of that block, increases the risk of bit errors developing. Good FTL solutions include strategies to handle these problems.
    • Fail-safety
      Conventional file systems are not fail-safe and often experience difficulties when common problems such as power loss or unexpected resets occur. Fail-safe flash tanslation layers can solve such challenges.