9.3.9 SMbus Alert Response

In latching comparator mode (COMP_LAT = 1), 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 pin reasserts. This assertion does not affect conversions that are already in progress. The ALERT/RDY pin is an open-drain output. This architecture allows several devices to share the same interface bus. When disabled, the pin holds a high state so that the pin does not interfere with other devices on the same bus line.

When the master senses that the ALERT/RDY pin has latched, the master issues an SMBus alert command (00011001) to the I²C bus. Any ADS1114 and ADS1115 data converters on the I²C bus with the ALERT/RDY pins asserted respond to the command with the slave address. If more than one ADS111x 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 master 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 1 if signals exceed the high threshold, and a 0 if signals exceed the low threshold.