INF-8077i XFP register map

An XFP module answers at one two-wire address (A0h) with a lower memory of 128 bytes — thresholds, flags, monitors and control — and upper tables selected by byte 127, of which table 01h is the serial ID. The layout predates SFF-8636 and was its model: the QSFP identity block copies XFP's byte positions almost exactly. This page lists the lower memory and table 01h byte by byte and bit by bit, compiled against INF-8077i Rev 4.5. Narrative: INF-8077i — XFP management.

Legend: rsvd = reserved · vendor = vendor specific · 16-bit values are MSB first · flags are latched, cleared on read.

Lower memory — thresholds, bytes 0–57

Byte	Field	Notes
0	Identifier	06h = XFP
1	Signal conditioner control	7 Tx CDR bypass? — bits control internal Tx/Rx CDR and loopbacks per Table 39: 7 Tx CDR off · 6 Tx amplitude/EQ control · 5–4 rsvd · 3 Rx CDR off · 2 line-side loopback · 1 XFI loopback · 0 rsvd (implementation advertised in table 01h byte 164)
2–3 / 4–5 / 6–7 / 8–9	Temperature high alarm / low alarm / high warning / low warning	signed 16-bit, 1/256 °C
10–17	rsvd	(thresholds for a second temperature in some drafts)
18–19 / 20–21 / 22–23 / 24–25	Tx bias HA / LA / HW / LW	unsigned 16-bit, 2 µA
26–27 / 28–29 / 30–31 / 32–33	Tx power HA / LA / HW / LW	unsigned 16-bit, 0.1 µW
34–35 / 36–37 / 38–39 / 40–41	Rx power HA / LA / HW / LW	unsigned 16-bit, 0.1 µW
42–43 / 44–45 / 46–47 / 48–49	AUX1 HA / LA / HW / LW	format per AUX1 type (table 01h byte 222)
50–57	AUX2 HA / LA / HW / LW	as AUX2 type

Lower memory — vendor, BER and wavelength control, bytes 58–79

Byte	Field	Contents
58–69	vendor	—
70	BER reporting	for modules with FEC: BER exponent/mantissa reporting control
71	Wavelength control — target MSB	tunable XFP: 71–72 wavelength set in 0.05 nm units
72	Wavelength control — target LSB	—
73–74	Wavelength error / status	reported wavelength offset in 0.005 nm units
75	Wavelength control flags	tuning in progress, unlocked, out of range
76–79	FEC control	enable/disable FEC, FEC status (10G FEC XFPs, ITU G.709 wrapped)

Lower memory — flags, bytes 80–95

Byte	Field	Bits
80	Alarm flags 1 (latched)	7 temp high alarm · 6 temp low alarm · 5 rsvd · 4 rsvd · 3 Tx bias high alarm · 2 Tx bias low alarm · 1 Tx power high alarm · 0 Tx power low alarm
81	Alarm flags 2 (latched)	7 Rx power high alarm · 6 Rx power low alarm · 5 AUX1 high alarm · 4 AUX1 low alarm · 3 AUX2 high alarm · 2 AUX2 low alarm · 1–0 rsvd
82	Warning flags 1 (latched)	same layout as byte 80 for warnings
83	Warning flags 2 (latched)	same layout as byte 81 for warnings
84	Status flags 1 (latched)	7 Tx_NR (not ready) · 6 Tx_Fault · 5 Tx CDR not locked · 4 Rx_NR · 3 Rx CDR not locked · 2 RX_LOS · 1 module not ready (Mod_NR) · 0 reset complete
85	Status flags 2 (latched)	7 APD supply fault · 6 TEC fault · 5 wavelength unlocked · 4–3 rsvd · 2 VCC5 fault? · 1 VCC3 fault · 0 VCC2 fault (supply-fault bits per implementation)
86–87	rsvd	—
88	Alarm masks 1	mask bits for byte 80
89	Alarm masks 2	for byte 81
90	Warning masks 1	for byte 82
91	Warning masks 2	for byte 83
92	Status masks 1	for byte 84
93	Status masks 2	for byte 85
94–95	rsvd	—

A set flag asserts the Interrupt pin unless masked; the host reads the flag bytes to clear them.

Lower memory — A/D readouts, bytes 96–109

Bytes	Monitor	Format
96–97	Temperature	signed 16-bit, 1/256 °C
98–99	rsvd	—
100–101	Tx bias	2 µA
102–103	Tx power	0.1 µW
104–105	Rx power	0.1 µW
106–107	AUX1	per type in table 01h byte 222
108–109	AUX2	per type

Lower memory — control and status, bytes 110–127

Byte	Field	Bits
110	General control/status	7 TX_DIS pin state · 6 soft TX_DIS (R/W) · 5 MOD_NR state · 4 P_Down state (pin) · 3 soft P_Down (R/W) · 2 Interrupt state · 1 RX_LOS state · 0 data not ready
111	General status 2	7 Tx_NR state · 6 Tx_Fault state · 5 Tx CDR not locked · 4 Rx_NR state · 3 Rx CDR not locked · 2 rsvd · 1 VPS (variable power supply) state · 0 rsvd (unlatched mirrors of byte 84)
112–117	vendor / rsvd	—
118	vendor	—
119–122	vendor	often password change area
123–126	vendor	often password entry area (same offsets as QSFP) — Write-protection types
127	Table select	01h serial ID (default) · 02h–7Fh rsvd · 80h–FFh vendor

Table 01h — serial ID, bytes 128–191 (covered by CC_BASE)

Byte	Field	Contents
128	Identifier	06h XFP
129	Extended identifier	7–6 rsvd · 5–4 power level: 00 ≤ 1.5 W · 01 ≤ 2.5 W · 10 ≤ 3.5 W · 11 > 3.5 W · 3 CDR (0 = XFI with CDR, 1 = no CDR) · 2 CLEI code present in table 01h? (bit 2 = CLEI in table 02h) · 1 Tx reference clock input required · 0 rsvd
130	Connector	SFF-8024 Table 4-3 (07h LC · 01h SC · 21h copper pigtail · 22h RJ45)
131	10G Ethernet compliance	7 10GBASE-SR · 6 10GBASE-LR · 5 10GBASE-ER · 4 10GBASE-LRM · 3 10GBASE-SW · 2 10GBASE-LW · 1 10GBASE-EW · 0 rsvd
132	10G Fibre Channel compliance	7 1200-MX-SN-I · 6 1200-SM-LL-L · 5 extended reach 1550 nm · 4 intermediate reach 1300 nm FP · 3–0 rsvd
133	10G copper links	7–0 rsvd (defined for future copper XFP)
134	Lower-speed links	7 1000BASE-SX / 1×FC MMF · 6 1000BASE-LX / 1×FC SMF · 5 2×FC MMF · 4 2×FC SMF · 3 OC-48 SR · 2 OC-48 IR · 1 OC-48 LR · 0 rsvd
135	SONET/SDH interconnect	7 I-64.1r · 6 I-64.1 · 5 I-64.2r · 4 I-64.2 · 3 I-64.3 · 2 I-64.5 · 1–0 rsvd
136	SONET/SDH short haul	7 S-64.1 · 6 S-64.2a · 5 S-64.2b · 4 S-64.3a · 3 S-64.3b · 2 S-64.5a · 1 S-64.5b · 0 rsvd
137	SONET/SDH long haul	7 L-64.1 · 6 L-64.2a · 5 L-64.2b · 4 L-64.2c · 3 L-64.3 · 2 G.959.1 P1L1-2D2 · 1–0 rsvd
138	SONET/SDH very long haul	7 V-64.2a · 6 V-64.2b · 5 V-64.3 · 4–0 rsvd
139	Encoding	7 64B/66B · 6 8B/10B · 5 SONET scrambled · 4 NRZ · 3 RZ · 2–0 rsvd (bit field, not an SFF-8024 value)
140	Bit rate minimum	units of 100 Mb/s (e.g. 5Fh = 9.5 Gb/s)
141	Bit rate maximum	units of 100 Mb/s (e.g. 6Fh = 11.1 Gb/s) — the pair defines the supported rate window
142	Length SMF	km
143	Length E-50 µm (OM3)	units of 2 m
144	Length 50 µm	units of 1 m
145	Length 62.5 µm	units of 1 m
146	Length copper	units of 1 m
147	Device technology	7–4 transmitter: 0h 850 nm VCSEL · 1h 1310 nm VCSEL · 2h 1550 nm VCSEL · 3h 1310 nm FP · 4h 1310 nm DFB · 5h 1550 nm DFB · 6h 1310 nm EML · 7h 1550 nm EML · 8h copper · 9h–Fh rsvd · 3 wavelength control (active) · 2 cooled transmitter · 1 detector (1 = APD, 0 = PIN) · 0 tunable
148–163	Vendor name	16 ASCII
164	CDR support	7 9.95 Gb/s · 6 10.3 Gb/s · 5 10.5 Gb/s · 4 10.7 Gb/s · 3 11.1 Gb/s · 2 rsvd · 1 line-side loopback supported · 0 XFI loopback supported
165–167	Vendor OUI	—
168–183	Vendor PN	16 ASCII
184–185	Vendor rev	2 ASCII
186–187	Wavelength	units of 0.05 nm (1310.00 nm = 26 200 = 6658h)
188–189	Wavelength tolerance	units of 0.005 nm
190	Max case temperature	°C
191	CC_BASE	(Σ bytes 128–190) mod 256

Table 01h — extended ID, bytes 192–255

Byte	Field	Contents
192	Max power dissipation	units of 20 mW (e.g. 7Dh = 2.5 W)
193	Total power in power-down	units of 20 mW
194	Max current	7–4 on +5 V in 50 mA units · 3–0 on +3.3 V in 100 mA units
195	Max current	7–4 on +1.8 V in 100 mA units · 3–0 on −5.2 V in 50 mA units
196–211	Vendor SN	16 ASCII
212–219	Date code	`YYMMDD` + 2 lot
220	Diagnostic monitoring type	7–5 rsvd · 4 Rx power measurement: 1 = average, 0 = OMA · 3 BER reporting supported · 2–0 rsvd
221	Enhanced options	7 VPS supported (variable power supply) · 6 soft TX_DISABLE implemented · 5 soft P_Down implemented · 4 VPS LV regulator mode · 3 VPS bypassed regulator mode · 2 active FEC control functions · 1 wavelength tunability implemented · 0 CMU (clock multiplier unit) supported
222	AUX monitoring	7–4 AUX1 type · 3–0 AUX2 type: 0 not implemented · 1 APD bias voltage (10 mV) · 2 rsvd · 3 TEC current (0.1 mA, signed) · 4 laser temperature (1/256 °C) · 5 laser wavelength (0.05 nm? — per spec: wavelength offset) · 6 +5 V supply (100 µV) · 7 +3.3 V supply · 8 +1.8 V supply · 9 −5.2 V supply · Ah +5 V current (100 µA) · Bh rsvd · Ch +3.3 V current · Dh +1.8 V current · Eh −5.2 V current · Fh rsvd
223	CC_EXT	(Σ bytes 192–222) mod 256
224–255	Vendor specific	not checksummed

Tables 02h–FFh

Table	Contents
02h	user EEPROM / CLEI code (when advertised)
03h–7Fh	rsvd
80h–FFh	vendor specific (often passwords, calibration backups)

What the QSFP inherited

Compare with the SFF-8636 upper page 00h map: bytes 128–130, 140–147 (lengths and technology nibble), 148–191 (vendor block, wavelength, CC_BASE), 196–223 (SN, date, CC_EXT) sit at the same offsets. The differences are the compliance bytes (131–138 redefined for 40/100G Ethernet), byte 139 (encoding as a value rather than a bit field) and 192–195 (power/current replaced by extended compliance and options). A tool that knows one map reads the other with a small translation table.

INF-8077i narrative — practical differences and X2/XENPAK.
SFF-8472 A2h map — the SFP diagnostics device for comparison.
Memory map quick reference.