8.6.3 Limit Registers

The TMP43x have registers for setting comparator limits for both the local and remote measurement channels. These registers have read and write capability. The High and Low Limit Registers for both channels span two registers, as do the temperature registers. These registers are only compared to at the end of every conversion cycle, and not immediately after updating the register value. The local temperature high limit is set by writing the high byte to pointer address 0Bh and writing the low byte to pointer address 16h for the TMP431 and 3Dh for the TMP432, or by using a single two-byte write command (high byte first) to pointer address 0Bh.

The local temperature high limit is obtained by reading the high byte from pointer address 05h and the low byte from pointer address 16h for the TMP4341 and 3Dh for the TMP432, or by using a two-byte read command from pointer address 05h. The power-on reset value of the local temperature high limit is 55h, 00h (85°C in standard temperature mode; 21°C in extended temperature mode).

Similarly, the local temperature low limit is set by writing the high byte to pointer address 0Ch and writing the low byte to pointer address 17h for the TMP431 and 3Eh for the TMP432, or by using a single two-byte write command to pointer address 0Ch. The local temperature low limit is read by reading the high byte from pointer address 06h and the low byte from pointer address 17h and 3Eh for the TMP432, or by using a two-byte read from pointer address 06h. The power-on reset value of the local temperature low limit register is 00h, 00h (0°C in standard temperature mode; –64°C in extended mode).

The remote temperature high limit for the TMP431 (remote temperature1 high limit for the TMP432) is set by writing the high byte to pointer address 0Dh and writing the low byte to pointer address 13h, or by using a two-byte write command to pointer address 0Dh. The remote temperature high limit is obtained by reading the high byte from pointer address 07h and the low byte from pointer address 13h, or by using a two-byte read command from pointer address 07h. The power-on reset value of the Remote Temperature High Limit Register is 55h, 00h (85°C in standard temperature mode; 21°C in extended temperature mode).

The remote temperature low limit for the TMP431 (remote temperature1 low limit for the TMP432) is set by writing the high byte to pointer address 0Eh and writing the low byte to pointer address 14h, or by using a two-byte write to pointer address 0Eh. The remote temperature low limit is read by reading the high byte from pointer address 08h and the low byte from pointer address 14h, or by using a two-byte read from pointer address 08h. The power-on reset value of the Remote Temperature Low Limit Register is 00h, 00h (0°C in standard temperature mode; –64°C in extended mode).

The remote temperature2 high limit for the TMP432 is set by writing the high byte to pointer address 15h and writing the low byte to pointer address 17h, or by using a two-byte write command to pointer address 15h. The remote temperature high limit is obtained by reading the high byte from pointer address 15h and the low byte from pointer address 17h, or by using a two-byte read command from pointer address 15h. The power-on reset value of the Remote Temperature High Limit Register is 55h, 00h (85°C in standard temperature mode; 21°C in extended temperature mode).

The remote temperature2 low limit for the TMP432 is set by writing the high byte to pointer address 16h and writing the low byte to pointer address 18h, or by using a two-byte write to pointer address 16h. The remote temperature low limit is read by reading the high byte from pointer address 16h and the low byte from pointer address 18h, or by using a two-byte read from pointer address 16h. The power-on reset value of the Remote Temperature Low Limit Register is 00h, 00h (0°C in standard temperature mode; –64°C in extended mode).

The TMP43x also have a THERM limit register for both the local and the remote channels. These registers are eight bits and allow for THERM limits set to 1°C resolution. The local channel THERM limit is set by writing to pointer address 20h. The remote channel THERM limit is set by writing to pointer address 19h. The remote channel THERM2 limit for the TMP432 is set by writing to pointer address 1Ah.

The local channel THERM limit is obtained by reading from pointer address 20h; the remote channel THERM limit is read by reading from pointer address 19h. The remote channel THERM2 limit is read by reading from pointer address 1Ah. The power-on reset value of the THERM limit registers is 55h for the TMP431A, TMP431B, TMP432A, and TMP432B (85°C in standard temperature mode; 21°C in extended temperature mode). The power-on reset value of the THERM limit registers is 69h for the TMP431C and TMP431D (105°C in standard temperature mode; 41°C in extended temperature mode). The THERM limit comparators also have hysteresis. The hysteresis of both comparators is set by writing to pointer address 21h. The hysteresis value is obtained by reading from pointer address 21h. The value in the Hysteresis Register is an unsigned number (always positive). The power-on reset value of this register is 0Ah (+10°C).