Accessing a particular register on the TMP1075 device is accomplished by writing the appropriate value to the pointer register. After Reset, the register value is set to zero. The value for the pointer register is the first byte transferred after the device address byte with the R/W bit low. Every write operation to the TMP1075 requires a value for the pointer register (see Figure 9-3).

When reading from the TMP1075 device, 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 action is accomplished by issuing a device address byte with the R/ W bit low, followed by the pointer register byte. No additional data are required. The host can then generate a START condition and send the device address byte with the R/ W bit high to initiate the read command. See Figure 9-5 for details of this sequence. If repeated reads from the same register are desired, the pointer register bytes do not have to be continually sent because the TMP1075 remembers the pointer register value until the value is changed by the next write operation.

Register bytes are sent MSB first.