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Codiode/Problems/Sequential Logic

Depth Constraints of Gray Code Pointers

MediumLogic CircuitAnalyze

Asynchronous FIFOs rely on Gray code pointers to safely pass state across clock domains without multi-bit transition errors. The system shown is a standard asynchronous FIFO with a depth of D = 8 entries. The write pointer wr_ptr and read pointer rd_ptr are implemented as Gray code counters. Determine the required bit width for these pointers and trace the specific Gray code values that indicate full and empty conditions. Evaluate the logic required to distinguish between an empty FIFO and a full FIFO when the read and write pointers wrap around.

Constraints

  • Pointer widths must accommodate the full range of depth plus one extra bit for wrap-around detection.
  • The FIFO depth D is strictly a power of 2.

Topics

fifogray-codeclock-domain-crossingpointers

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