SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
The UCD3138 PMBus interface provides an automated handling of the ALERT Response. To enable it, set the ALERT_EN bit in PMBCTRL3. This will pull the ALERT pin low, and enable the ALERT response from the hardware. If MAN_SLAVE_ACK is not set, the hardware will automatically acknowledge the special ALERT address, and will automatically to the arbitration with the device address. If the UCD wins the arbitration, it will automatically release the ALERT line and clear the ALERT_EN bit.
In manual address acknowledge mode (MAN_SLAVE_ACK is set), the firmware must read the received address from the Receive Data Register and transmit the desired slave address back to the Master. The firmware must check for LOST_ARB, and clear the ALERT_EN bit if the arbitration is won.