When bit 0 of the Filter_Alert_Mode Register is set to 0, the Interrupt/ SMBus Alert mode is enabled. In this mode, the ALERT pin is asserted at the end of a conversion cycle if the measured temperature exceeds a High Alert Limit or goes below a Low Alert Limit defined in the limit registers. In this mode, the TMP4718 sets the ALERT mask bit of the Configuration Register during a read of the Status Register if any flag in Status Register, except the ADC_Busy flag and Remote Diode Open flag, is set. This prevents the ALERT pin from triggering until the controller resets the ALERT mask bit (write 0 to Alert_MSK bit).

The ALERT High Status flags set at the end of a conversion cycle when the measured temperature exceeds a High Alert Limit register limit. There are separate High Limit values and status register flags for the remote and local temperature measurements. The status register flags will only set to their respective temperature measurements.

The Remote ALERT Low Status flag sets at the end of a conversion cycle when the measured remote temperature is below the Remote Low Alert Limit register limit.

The Status Register limit flags are cleared after a read command of the Status Register from the controller and are set again at the end of a proceeding temperature conversion cycle if the measured temperature is outside the set limits.

When the ALERT pin is connected to the SMBus alert line, there can be multiple devices on the same output. For the controller to resolve which target is generating an alert, the controller can send a SMBus ALERT Response Address (ARA) command. If the TMP4718 is generating an alert and an ARA command is sent, the TMP4718 sets the ALERT MASK bit in the Configuration register and send the target address to the controller. An ARA command will not clear any Status register flags.

Figure 8-15 shows the behavior of the ALERT pin and flags while in SMBus Alert mode.

Figure 8-15 Alert SMBus Mode Timing Diagram