SNIS237A December 2024 – April 2025 TMP118
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
For a read operation the controller sends a START condition, followed by the target address with the R/W bit set to 0b (signifying a write). The target acknowledges the write request, and the controller then sends the register pointer in the next frame. The controller then initiates a START or RESTART followed by the target address with the R/W bit set to 1b (signifying a read). A START initiates communication with an target, while a RESTART allows the controller to access different registers on the same target without needing to send a full STOP signal first. The controller continues to send out clock pulses but releases the SDA line so that the target can transmit data. At the end of every byte of data, the controller sends an ACK to the target, letting the target know that the controller is ready for more data. Once the controller has received the number of bytes the controller is expecting, the controller sends a NACK, signaling to the target to halt communications and release the SDA line. The controller follows this up with a STOP condition.
Note that:
If the controller needs to read from the same register repeatedly, the controller is not required to resend the pointer over and over again. The pointer value is stored in the device.
The default pointer value upon device POR is 0h, so the controller can immediately proceed to read the temperature result after device power-up without sending the pointer value for the Temp_Result register.
Figure 7-16 shows an example of reading a single word from a target register.