7.3.4.1 Writing and Reading to the TMP275

Accessing a particular register on the TMP275 is accomplished by writing the appropriate value to the Pointer Register. The value for the Pointer Register is the first byte transferred after the slave address byte with the R/W bit LOW. Every write operation to the TMP275 requires a value for the Pointer Register (see Figure 8).

When reading from the TMP275, the last value stored in the Pointer Register by a write operation is used to determine which register is read by a read operation. To change the register pointer for a read operation, a new value must be written to the Pointer Register. This is accomplished by issuing a slave address byte with the R/W bit LOW, followed by the Pointer Register Byte. No additional data is required. The master can then generate a START condition and send the slave address byte with the R/W bit HIGH to initiate the read command. See Figure 9 for details of this sequence. If repeated reads from the same register are desired, it is not necessary to continually send the Pointer Register bytes, as the TMP275 remembers the Pointer Register value until it is changed by the next write operation.

Note that register bytes are sent most-significant byte first, followed by the least significant byte.