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Codiode/Problems/Sequential Logic

UART Transmitter Start Bit

EasyLogic CircuitBuild

Asynchronous serial communication requires a synchronization edge to wake up the receiver. The UART transmitter achieves this by pulling the line low for exactly one baud duration before sending the data payload.

Implement a state machine that generates a UART start bit. The circuit operates on a baud rate clock and uses a synchronous active-high rst. The system has three states: IDLE, START, and DATA.

When rst is asserted, the system synchronously returns to the IDLE state.

| State | start_tx | Next State | tx_out | data_state | |---------|------------|--------------|----------|--------------| | IDLE | 0 | IDLE | 1 | 0 | | IDLE | 1 | START | 1 | 0 | | START | 0 | DATA | 0 | 0 | | START | 1 | DATA | 0 | 0 | | DATA | 0 | DATA | 1 | 1 | | DATA | 1 | DATA | 1 | 1 |

Constraints

  • Implement a Moore state machine.
  • Use D flip-flops for state storage.
  • The rst signal must be synchronous and active-high.

Topics

fsmstate-machineuart

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Place the gates, wire them up and watch the signals settle. Every submission runs on the same simulation engine that grades it.

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