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Hardware interview practice

Identify Legal I2C Data and Acknowledge Timing

EasyFirmwareC

An I2C controller is transmitting one address byte while SCL is driven normally and no clock stretching occurs. Which bus rule is correct?

Choose one

Answer choices

  1. A. The transmitter always drives both SDA high and low actively, so arbitration is impossible.
  2. B. SDA must remain stable while SCL is high except for START or STOP; the receiver acknowledges by pulling SDA low during the ninth clock pulse.
  3. C. SDA may change freely while SCL is high, and ACK is a high SDA level on the eighth clock.
  4. D. START occurs when SDA rises while SCL is low, and STOP occurs when SDA falls while SCL is low.