In latching comparator mode (COMP_LAT = 1b), the ALERT/RDY pin asserts when the comparator detects a conversion that exceeds the upper or lower threshold value. This assertion is latched and can be cleared only by reading conversion data, or by issuing a successful SMBus alert response and reading the asserting device I²C address. If conversion data exceed the upper or lower threshold values after being cleared, the ALERT/RDY pin reasserts. This assertion does not affect conversions that are already in progress. The open-drain ALERT/RDY output allows several devices to share the same interface bus. When disabled, the ALERT/RDY pin holds a high state so that the pin does not interfere with other devices on the same bus line.

When the controller senses that the ALERT/RDY pin has latched, the controller issues an SMBus alert command (00011001b) to the I²C bus. Any ADS111xL devices on the I²C bus with the ALERT/RDY pins asserted respond to the command with the target address. If more than one ADS111xL on the I²C bus assert the latched ALERT/RDY pin, arbitration during the address response portion of the SMBus alert determines which device clears assertion. The device with the lowest I²C address always wins arbitration. If a device loses arbitration, the device does not clear the comparator output pin assertion. The controller then repeats the SMBus alert response until all devices have the respective assertions cleared. In window comparator mode, the SMBus alert status bit indicates a 1b if signals exceed the high threshold, and a 0b if signals exceed the low threshold.