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Codiode/Problems/Sequential Logic

I2C Stop Condition Detector

MediumLogic CircuitBuild

Every I2C slave device monitors the bus to determine when a transaction concludes and the bus is free. The stop condition is the universal signal that a master has released the bus.

The detector must monitor the serial clock SCL and serial data SDA lines. It asserts the Stop output for exactly one clock cycle when SDA transitions from 0 to 1 while SCL is strictly 1. All signals are synchronous to the implicit system clock.

| rst | SCL | SDA_prev | SDA_curr | Stop | |-------|-------|------------|------------|--------| | 1 | X | X | X | 0 | | 0 | 0 | X | X | 0 | | 0 | 1 | 0 | 0 | 0 | | 0 | 1 | 0 | 1 | 1 | | 0 | 1 | 1 | 1 | 0 | | 0 | 1 | 1 | 0 | 0 |

Constraints

  • Use standard D flip-flops for state storage.
  • The reset signal rst is synchronous and active-high.
  • The Stop output must assert for exactly one clock cycle per valid transition.

Topics

Edge DetectionProtocolI2C

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