INF-8077i — XFP management (+ X2, XENPAK)

Three 10-gigabit form factors predate SFP+. Only one of them — XFP — remains common in the field, and it uses a management interface that is neither SFF-8472 nor SFF-8636. Reading an XFP with the wrong map produces plausible-looking garbage, so this document matters to anyone coding 10G modules.

The documents

X2 and XENPAK are large, legacy modules for early 10GbE switches with a parallel XAUI electrical interface; XFP introduced the clean serial XFI interface and an in-module CDR.

INF-8077i memory map

XFP management lives at two-wire address A0h and is organised as:

• Lower memory (bytes 0–127) — always accessible: control/status bits, the

digital diagnostics (temperature, Tx bias, Tx/Rx power, supply voltages) and their alarm/warning thresholds, flags and masks.

• Upper memory tables (bytes 128–255) — selected by a **table-select byte at

address 127**:

• Table 01h — serial ID: identifier, vendor, part number, serial, dates,

transceiver codes, wavelength, CDR/rate capabilities, and the checksums.

• Table 02h — user-writable EEPROM.
• Vendor-specific tables — including DWDM tuning registers on tunable XFPs.

The structure resembles the later paged model of SFF-8636 (a table select at byte 127) but the field positions are XFP-specific, and diagnostics sit in lower memory rather than a separate A2h block as in SFF-8472.

Practical differences

In CodingBox

CodingBox applies the INF-8077i map for XFP: identity from Table 01h, thresholds and DDM from lower memory, with checksums recalculated on write. It is one of the five MSA specification families the application decodes. See also XFP.

Source

• sfptotal.ru — List of MSA standards and specifications; SNIA SFF library