Local and Remote Temperature Registers

I/O

Control

Interface

Pointer Register

Configuration Register

Status Register

Local and Remote Temperature Limit Registers

Conversion Rate Register

Remote Temperature Offset Registers

One-Shot Start Register

Local and Remote THERM Limit Registers

THERM Hysteresis Register

N-factor Correction Register

Consecutive ALERT Register

Digital Filter Register

Manufacturer ID Register

SDA

SCL

TMP451-Q1

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SLOS877 – OCTOBER 2014

7.6.1 Register Information

The TMP451-Q1 device contains multiple registers for holding configuration information, temperature

measurement results, and status information. These registers are described in Figure 17 and Table 3.

7.6.1.1 Pointer Register

Figure 17 shows the internal register structure of the TMP451-Q1 device. The 8-bit pointer register is used to

address a given data register. The pointer register identifies which of the data registers should respond to a read

or write command on the two-wire bus. This register is set with every write command. A write command must be

issued to set the proper value in the pointer register before executing a read command. Table 3 describes the

pointer register and the internal structure of the TMP451-Q1 registers. The power-on reset (POR) value of the

pointer register is 00h (0000 0000b).

Figure 17. Internal Register Structure

7.6.1.2 Temperature Registers

The TMP451-Q1 device has multiple 8-bit registers that hold temperature measurement results. The eight most

significant bits (MSBs) of the local temperature sensor result are stored in register 00h, while the four least

significant bits (LSBs) are stored in register 15h (the four MSBs of register 15h). The eight MSBs of the remote

temperature sensor result are stored in register 01h, and the four LSBs are stored in register 10h (the four MSBs

of register 10h). The four LSBs of both the local sensor and the remote sensor indicate the temperature value

after the decimal point (for example, if the temperature result is 10.0625

˚C, the high byte is 0000 1010 and the

low byte is 0001 0000). These registers are read-only and are updated by the ADC each time a temperature

measurement is completed.

When the full temperature value is needed, reading the MSB value first causes the LSB value to be locked (the

ADC does not write to it) until it is read. The same thing happens upon reading the LSB value first (the MSB

value is locked until it is read). This mechanism assures that both bytes of the read operation are from the same

ADC conversion. This assurance remains valid only until another register is read. For proper operation, read the

high byte of the temperature result first. Read the low byte register in the next read command; if the LSBs are not

needed, the register may be left unread. The power-on reset value of all temperature registers is 00h.

Copyright © 2014, Texas Instruments Incorporated

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