JAJSMF5B september 2022 – june 2023 TPS25990
PRODUCTION DATA
When there are multiple target devices on the bus with their SMBA# pins also tied together, if one or more target devices assert the SMBA#, the host controller needs a way to identify those target devices on the bus. It does so using the ARA mechanism, which is initiated by sending a read command to the ARA broadcast address 0x0C.
The ARA Automatic Mask is a mask that is set in response to a successful ARA read. An ARA read operation returns the PMBus® address of the lowest addressed target device on the bus that has its SMBA# asserted. A successful ARA read means that this target device was the one that returned its address. When a target device responds to the ARA read, it releases the SMBA# signal. When the last target device on the bus that has an SMBA# set has successfully reported its address, the SMBA# signal will de-asserted.
The way that the TPS25990 releases the SMBA# signal is by setting the ARA Automatic mask bit for all fault conditions present at the time of the ARA read. All status registers will still show the fault condition, but it will not generate an SMBA# alert on that fault again until the ARA Automatic mask is cleared by the host issuing the CLEAR_FAULTS command to this part. This must be done as a routine part of servicing an SMBA# condition on a part, even if the ARA read is not done.