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Codiode/Problems/Sequential Logic

Start Bit Detection Waveform

MediumLogic CircuitTiming Diagram

A positive-edge-triggered UART receiver detects a LOW start bit on the serial line and shifts in 8 subsequent data bits before pulsing a valid signal.

Three signals are shown: CLK (clock, period 2), RX (serial input, idle HIGH), and STROBE (output, initially 0).

Trace STROBE across all 24 time steps.

Constraints

  • The receiver evaluates inputs strictly on the LOW-to-HIGH transition of CLK.
  • The start bit is detected on the first rising edge where RX is sampled LOW.
  • The 8 data bits are sampled on the 8 rising edges immediately following start bit detection.
  • STROBE must be asserted HIGH for exactly one clock cycle immediately after the 8th data bit is sampled.

Topics

state-machineshift-registersuartedge-detection

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