EEPROM memory map quick reference

The one-page byte map for the three memory layouts CodingBox works with most: SFF-8472 (SFP class), SFF-8636 (QSFP+/QSFP28) and CMIS (QSFP-DD, OSFP, QSFP112, SFP-DD). Use it to find a field fast in the EEPROM editor; the editor names every byte on hover, and the specification documents remain the authority for edge cases.

Positions follow the current public revisions (SFF-8472 rev 12.x, SFF-8636 rev 2.x, CMIS 5.x). Older modules may implement earlier revisions — check the compliance byte.

SFF-8472 — A0h (serial ID)

Bytes	Field	Notes
0	Identifier	03h = SFP/SFP+/SFP28 (SFF-8024)
1	Extended identifier	04h = MOD_DEF 4 (two-wire ID)
2	Connector	07h LC, 01h SC, 0Ch MPO, 21h copper, 23h no separable
3–10	Transceiver compliance codes	Ethernet 10G (3), SONET (4–5), Ethernet 1G (6), FC (7–10)
11	Encoding	64b/66b, 8b/10b, NRZ…
12	Nominal signalling rate	×100 Mb/s (103 = 10.3 Gb/s)
13	Rate identifier	rate-select scheme (SFF-8079)
14	Length SMF	km
15	Length SMF	×100 m
16	Length 50 µm OM2	×10 m
17	Length 62.5 µm OM1	×10 m
18	Length OM4 or copper	m
19	Length OM3	×10 m
20–35	Vendor name	ASCII, space-padded
36	Extended compliance code	SFF-8024 Table 4-4
37–39	Vendor OUI	IEEE company ID
40–55	Vendor part number	ASCII
56–59	Vendor revision	ASCII
60–61	Wavelength (nm) or cable compliance	1310 = 051Eh
62	Fibre Channel speed 2 / unallocated	—
63	CC_BASE	checksum of bytes 0–62
64–65	Options	TX_DISABLE, TX_FAULT, RX_LOS, rate select…
66–67	Signalling rate max / min	% above / below nominal
68–83	Vendor serial number	ASCII
84–91	Date code	YYMMDDLL
92	Diagnostic monitoring type	bit 6 DDM, bit 5 internal cal, bit 4 external cal, bit 3 average/OMA
93	Enhanced options	alarm/warning flags, soft TX_DISABLE, soft rate select
94	SFF-8472 compliance	revision the module follows
95	CC_EXT	checksum of bytes 64–94
96–127	Vendor specific	—
128–255	Reserved (SFF-8079)	—

SFF-8472 — A2h (diagnostics)

Bytes	Field	Notes
0–39	Thresholds	temp, Vcc, bias, Tx pwr, Rx pwr — each HA, LA, HW, LW (details)
40–55	Optional thresholds	laser temp, TEC current
56–91	External calibration constants	Rx power polynomial, slopes/offsets (details)
92–94	Reserved	—
95	CC_DMI	checksum of bytes 0–94
96–105	Real-time monitors	temp, Vcc, Tx bias, Tx pwr, Rx pwr (units)
106–109	Optional monitors	laser temp / TEC
110	Status / control	TX_DISABLE state, RS0/RS1, TX_FAULT, RX_LOS, data ready
111	Reserved	—
112–113	Alarm flags	—
114–115	Optional controls	Tx input EQ / Rx output emphasis
116–117	Warning flags	—
118–119	Extended status / control	soft RS, power level
120–126	Vendor specific	password area 0x7B–0x7E (123–126) on protected modules (write protection)
127	Table / page select	selects optional upper tables
128–247	User EEPROM (Table 00h)	writable scratch area
248–255	Vendor control	—

SFF-8636 — lower page 00h (QSFP+/QSFP28)

Bytes	Field
0	Identifier (0Dh QSFP+, 11h QSFP28)
1	Revision compliance
2	Status: data-not-ready, IntL, flat memory
3	Tx LOS (7–4) / Rx LOS (3–0)
4	Tx adaptive-EQ fault / Tx fault
5	Tx LOL / Rx LOL (CDR)
6–7	Temperature / Vcc alarm-warning flags
9–14	Per-lane Rx power, Tx bias, Tx power flags
22–23	Module temperature
26–27	Module Vcc
34–41	Rx power, lanes 1–4
42–49	Tx bias, lanes 1–4
50–57	Tx power, lanes 1–4
86	Tx disable per lane
87 / 88	Rx / Tx rate select
93	Power control (low-power, override)
98	CDR control (Tx 7–4, Rx 3–0)
100–106	Interrupt masks
119–122	Password change entry
123–126	Password entry (0x7B)
127	Page select

SFF-8636 — upper page 00h (identity)

Bytes	Field
128	Identifier
129	Extended identifier: power class, CDR present (bits 3/2), CLEI
130	Connector
131–138	Specification compliance (Ethernet, SONET, SAS, GbE, FC)
139	Encoding
140	Nominal bit rate (×100 Mb/s; FFh → see 222)
141	Extended rate select compliance
142	Length SMF (km)
143	Length OM3 (×2 m)
144 / 145	Length OM2 / OM1 (m)
146	Length copper or OM4 (m)
147	Device technology (laser type, cooled, tunable…)
148–163	Vendor name
164	Extended module codes (InfiniBand)
165–167	Vendor OUI
168–183	Vendor part number
184–185	Vendor revision
186–187	Wavelength (÷20 nm) or copper attenuation
188–189	Wavelength tolerance (÷200)
190	Max case temperature
191	CC_BASE (128–190)
192	Extended specification compliance (SFF-8024 Table 4-4)
193–195	Options
196–211	Vendor serial number
212–219	Date code
220	Diagnostic monitoring type
221	Enhanced options
222	Nominal bit rate (×250 Mb/s)
223	CC_EXT (192–222)
224–255	Vendor specific

Upper page 03h holds thresholds; page 02h user EEPROM; page 01h application select (SFF-8636).

CMIS — lower page and key pages

Location	Field
Lower 0	Identifier (18h QSFP-DD, 19h OSFP, 1Eh QSFP112, 1Ah SFP-DD)
Lower 1	CMIS revision (e.g. 50h = 5.0)
Lower 2	Module characteristics: flat memory, memory model
Lower 3	Module state (bits 3–1: 1 LowPwr, 2 PwrUp, 3 Ready, 4 PwrDn, 5 Fault)
Lower 8–13	Module flags
Lower 14–25	Module monitors (temp 14–15, Vcc 16–17, aux)
Lower 26	Module global controls (low-power, software reset)
Lower 118–121	Password change
Lower 122–125	Password entry
Lower 126	Bank select
Lower 127	Page select
Page 00h 128–255	Identity: vendor 129–144, OUI 145–147, PN 148–163, rev 164–165, SN 166–181, date 182–189, CLEI 190–199, power class 200–201, connector 203, media type 212…
Page 01h	Advertisements: monitors implemented, CDR support, VDM, applications (86–117)
Page 02h	Thresholds
Page 10h	Lane controls: data-path, Tx disable, CDR enable (160/161), application select
Page 11h	Lane status and monitors: flags 134–153, Tx power 154–169, Tx bias 170–185, Rx power 186–201
Pages 20h–2Fh	VDM (Per-lane diagnostics)
Pages 9Fh, A0h+	CDB command / reply

Full description: CMIS, MIS for SFP-DD.

Checksums

Checksum	Covers	Where
CC_BASE (SFP)	A0h 0–62	A0h 63
CC_EXT (SFP)	A0h 64–94	A0h 95
CC_DMI (SFP)	A2h 0–94	A2h 95
CC_BASE (QSFP)	128–190	191
CC_EXT (QSFP)	192–222	223
CMIS page checksums	per page	last byte of the page

All are simple 8-bit sums. CodingBox recalculates them automatically on every write — a hand-edited dump with a stale checksum is rejected by most hosts (EEPROM recoding).

Protocol-level view of how these bytes are reached — addresses, paging, banks, timing: Two-wire interface. Which bytes each checksum covers and how to compute them: Checksums.