SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
If a PMBus message to the UCD accesses the reserved address of 0x7f, the UCD may begin a test mode entry sequence. It may hold the data line low. In this case, additional transitions on the PMBus clock line will return the PMBus to normal functionality. On the UCD3138128/A64 and the A versions of the same device, the test mode entry address is 0x7e. This is less likely to occur as a fault case.