ZHCS916I March 2009 – December 2018 TMP112
The temperature limits are stored in the T(LOW) and T(HIGH) registers in the same format as the temperature result, and their values are compared to the temperature result on every conversion. The outcome of the comparison drives the behavior of the ALERT pin, which operates as a comparator output or an interrupt, and is set by the TM bit in the configuration register.
In Comparator mode (TM = 0), the ALERT pin becomes active when the temperature equals or exceeds the value in the T(HIGH) register and generates a consecutive number of faults according to fault bits F1 and F0. The ALERT pin remains active until the temperature falls below the indicated T(LOW) value for the same number of faults.
In interrupt mode (TM = 1), the ALERT pin becomes active when the temperature equals or exceeds the value in T(HIGH) for a consecutive number of fault conditions (as shown in Table 11). The ALERT pin remains active until a read operation of any register occurs, or the device successfully responds to the SMBus alert response address. The ALERT pin is also cleared if the device is placed in shutdown mode. When the ALERT pin is cleared, it becomes active again only when temperature falls below T(LOW), and remains active until cleared by a read operation of any register or a successful response to the SMBus alert response address. When the ALERT pin is cleared, the above cycle repeats, with the ALERT pin becoming active when the temperature equals or exceeds T(HIGH). The ALERT pin can also be cleared by resetting the device with the general-call Reset command. This action also clears the state of the internal registers in the device, returning the device to comparator mode (TM = 0).
Both operating modes are represented in Figure 16. Table 12 and Table 13 list the format for the THIGH and TLOW registers. The most significant byte is sent first, followed by the least significant byte. The power-up reset values for T(HIGH) and T(LOW) are:
The format of the data for THIGH and TLOW is the same as for the Temperature Register.