SFF-8472 — SFP diagnostics

SFF-8472, the Diagnostic Monitoring Interface for Optical Transceivers, defines the management interface for SFP-class modules — SFP, SFP+ and SFP28. It builds on the SFP MSA identification memory and adds real-time diagnostics.

Two memory addresses

The module is read over a two-wire (I²C) interface at two addresses:

Address	Contents
A0h	Serial ID: identity, vendor, capabilities, connector, wavelength (256 bytes)
A2h	Diagnostics: live monitors, thresholds, alarm and warning flags

What A2h provides

Real-time monitors — temperature, supply voltage, laser bias current and optical

TX/RX power.

Thresholds — factory high/low alarm and warning limits for each monitor.
Flags — status bits that indicate when a value has crossed a threshold.

This is the data CodingBox presents on the Check transceiver and DDM screens. For what the diagnostic values mean, see DDM basics.

Not every SFP implements A2h diagnostics; a bit in A0h indicates whether digital diagnostics are supported.