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3

Sensor Operation

The STCC4 uses I2C communication based on the NXP I2C-bus specification and user manual12. Supported

I2C modes are Standard-mode, Fast-mode and Fast-mode Plus. Clock stretching is not supported.

3.1 I2C Address

The I2C address (I2C ADDR) for the STCC4 is 0x64. See Section 2.4 to select the alternative I2C address 0x65.

3.2 I2C Data Transfer Formats

The write, read and combined data transfer formats are visualized in Figure 2. Data and commands are

transferred in multiples of 16-bit words, with the most significant byte (MSB) transmitted first. All transfers

must begin with a start condition (S) and terminate with a stop condition (P). A sensor is addressed by sending

its 7-bit I2C address, followed by an eighth data direction bit denoting the communication direction (W/R):

“zero” indicates transmission to the target (i.e., “WRITE”) and “one” indicates a request for data (i.e., “READ”).

Data words are succeeded by an 8-bit checksum (cyclic redundancy check CRC-8, see Section 3.3). Command

words (CMD) contain a 3-bit CRC. In the write direction, the checksum must be transmitted. In read direction,

the master may abort transmission after any data byte by sending a not acknowledge (NACK) and a stop

condition. After receiving a command, the sensor requires the specified execution time before responding with

a ACK.

Figure 2. Write, read and combined data transfer formats

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NXP I2C-bus specification and user manual UM10204, Rev.7, 01 November 2021