tWR

tWR, or Write Recovery Time, is a timing parameter used in memory devices to denote the minimum interval after the end of a write operation before the memory can safely begin a new operation, such as another write or a subsequent read. The requirement exists because after a write, the memory cell and surrounding circuitry need time to settle and restore the stored charge, ensuring that the written data remains stable and is not corrupted by immediately following operations.

In DRAM and SDRAM contexts, tWR is part of JEDEC timing specifications and is defined relative to other timings such as tRP, tRCD, and tRC. The exact value of tWR depends on device technology, organization, operating frequency, voltage, and temperature; it is typically on the order of a few tens of nanoseconds in modern DRAM, with higher-speed devices having shorter recovery windows but still bounded by device limits. Memory controllers use tWR to schedule operations correctly and avoid data hazards, sometimes alongside related timings such as tWTR (write to read) in timing diagrams and profiles.

In NAND flash and other non-volatile memories, tWR may be defined as the minimum time after a program (write) operation before a read or another operation can be issued, with actual times often longer due to flash programming behavior and wear leveling.

Notes: The precise definition and value of tWR vary by device family and standard edition; always consult the relevant datasheet or JEDEC standard for exact figures.