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Re-transcribe BCM84891L MDIO command and SFP register excerpts in full (all 45 commands, complete serial-ID table); scrub doc-provenance attribution and label all our interjections as field notes

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# FS SFP-10G-T-100 transport reference — transcription
Transcribed (visually, tables intact) from the FS-provided 4-page
`10GBase-T Coper SFP Registers Operation's Reference for BCM84891.pdf`
(an ODM document — PDF metadata titles it "ABCU-5710RZ / ABCU-5700RZ").
Full visual transcription (tables intact) of a 4-page excerpt
`10GBase-T Coper SFP Registers Operation's Reference for BCM84891.pdf` (the pages are
numbered "Page N of 19", so this is a 4-page excerpt of a 19-page ODM document; PDF
metadata titles it "ABCU-5710RZ / ABCU-5700RZ"). Page banner:
"100/1000Base-T or 10/5/2.5GBase-T Copper SFP+ Transceiver; Cat 6a/7 up to 100 m at 10GBase;
Cat 5 or better up to 100 m at 100/1000Base; 0–70 °C or −40–85 °C."
## 1. Serial ID memory (A0h)
Cabletest field notes (shipped-unit deviations from the reference values, and findings) are
marked **Field note**.
Standard SFP MSA serial ID at I2C A0h. Notable factory values (the module is
honest about copper — cf. ../README.md):
## 1. Serial ID Memory Contents (I2C A0h)
| Addr | Field | Value | Meaning |
|---|---|---|---|
| 0 | Identifier | 03 | SFP |
| 1 | Ext. identifier | 04 | MOD4 |
| 2 | Connector | 21 | Copper pigtail (the shipped unit reads 22 = RJ45) |
| 3–10 | Transceiver | 02 00 00 00 00 08 00 00 | 10G Base-XFI to copper / SGMII to copper |
| 11 | Encoding | 00 | 64B/66B (or 8B/10B) |
| 12 | BR, nominal | 67 | 10.3125 GBd |
| 18 | Length (copper) | 64 | 100 m; 30 m minimum in-spec copper length |
| 20–35 | Vendor name | "OEM " | shipped unit reads "FS" |
| 40–55 | Vendor PN | "10GBase-T C100m" | shipped unit reads "SFP-10G-T-100" |
| 64–65 | Options | 00 12 | TX_DISABLE and RX_LOS implemented (shipped: 00 1A) |
| 92 | Diag monitoring | 00 | **no A2h DOM implemented** |
| 93 | Enhanced options | 00 | |
| 94 | SFF-8472 compliance | 00 | digital diagnostics not included |
| 96–127 | Vendor specific | all 00 | |
The 10GBase-T Copper SFP provides standard serial ID compliant with SFP MSA, accessed at
address A0h via the 2-wire serial CMOS EEPROM protocol.
## 2–3. SMI (I2C→MDIO) protocol for the PHY, with timing
### Base ID Fields
The PHY is a 2-wire device at 8-bit address **0xAC write / 0xAD read**
(`1010110x`). Clause-45 access frames:
| Addr | Size (B) | Field | Description / Contents | Hex |
|---|---|---|---|---|
| 0 | 1 | Identifier | Type of Serial transceiver (SFP) | 03 |
| 1 | 1 | Ext. Identifier | Extended identifier of type serial transceiver (MOD4) | 04 |
| 2 | 1 | Connector | Code of optical connector type (Copper) | 21 |
| 3–10 | 8 | Transceiver | 10G Base-XFI to Copper or SGMII to Copper | 02 00 00 00 00 08 00 00 |
| 11 | 1 | Encoding | 64B/66B (or 8B/10B) | 00 |
| 12 | 1 | BR, Nominal | Nominal baud rate, unit of 100 MBd (10.3125 GBd for 10GBase-T) | 67 |
| 13 | 1 | Rate Identifier | Type of rate select functionality (Unspecified) | 00 |
| 14 | 1 | Length (SMF9um)-km | Link length supported for single mode fiber, units of km | 00 |
| 15 | 1 | Length (SMF9um) | Link length supported for 9/125um fiber, units of 100m | 00 |
| 16 | 1 | Length (50um) | Link length supported for 50/125um OM2 fiber, units of 10m | 00 |
| 17 | 1 | Length (62.5um) | Link length supported for 62.5/125um OM1 fiber, units of 10m | 00 |
| 18 | 1 | Length (OM4 or copper cable) | Link length for 50um OM4 fiber, units of 10m. Alternatively copper or direct-attach cable, units of m. For copper links, specifies minimum link length (30m) supported while operating in compliance with applicable standards using copper cable. | 64 |
| 19 | 1 | Length (OM3) | Link length supported for 50um OM3 fiber, units of 10m | 00 |
| 20–35 | 16 | Vendor Name | SFP vendor name (ASCII) "OEM " | 4F 45 4D 20 20 20 20 20 20 20 20 20 20 20 20 20 |
| 36 | 1 | Transceiver | Code for electronic or optical compatibility | 00 |
| 37–39 | 3 | Vendor OUI | SFP vendor IEEE company ID; all zero = unspecified | 00 00 00 |
| 40–55 | 16 | Vendor PN | Part number (ASCII) "10GBase-T C100m" | 31 30 47 42 61 73 65 2D 54 20 42 21 30 30 6D 20 |
| 56–59 | 4 | Vendor rev | Revision (ASCII); all zero = unspecified (1.0 revision) | 31 2E 30 20 |
| 60–61 | 2 | Wavelength | Laser wavelength (Passive/Active Cable Spec Compliance). 00 for both bytes = wavelength/cable spec compliance unspecified. | 00 00 |
| 62 | 1 | Unallocated | | 00 |
| 63 | 1 | CC_BASE | Check code for Base ID Fields — LSB of checksum of addresses 0–62 | xx |
**Write (one I2C frame, 6 bytes):**
`S [0xAC] [000+DEVAD] [Reg_H] [Reg_L] [Data_H] [Data_L] P`
### Extended ID Fields
**Read (two I2C frames):**
`S [0xAC] [001+DEVAD] [Reg_H] [Reg_L] P` → **delay > 1 ms** →
`S [0xAD] [Data_H] [Data_L] P`
| Addr | Size (B) | Field | Description / Contents | Hex |
|---|---|---|---|---|
| 64–65 | 2 | Option | Which optional transceiver signals are implemented: TX_DISABLE and RX_LOS are implemented | 00 12 |
| 66 | 1 | BR, max | Upper bit-rate margin, units of %; 00 = not specified | 00 |
| 67 | 1 | BR, min | Lower bit-rate margin, units of %; 00 = not specified | 00 |
| 68–83 | 16 | Vendor SN | Serial number (ASCII) | xx… |
| 84–91 | 8 | Date code | Manufacturing date: Year (2B), Month (2B), Day (2B), vendor lot code, may be blank (2B) | xx… |
| 92 | 1 | Diagnostic Monitoring Type | Which type of diagnostic monitoring is implemented (if any) | 00 |
| 93 | 1 | Enhanced Options | Which optional enhanced features are implemented (if any) | 00 |
| 94 | 1 | SFF-8472 Compliance | Which SFF-8472 revision the transceiver complies with; 00 = digital diagnostics not included/undefined | 00 |
| 95 | 1 | CC_EX | Check code for Extended ID Fields (addresses 64–94) | xx |
Bit-level example diagrams confirm: every byte is slave-ACKed except the final
read data byte, which the master **NAKs** before STOP. Worked examples: write
0x55AA to 1.0xA820; read 0x8542 from 1.0x0003.
### Vendor Specific ID Fields
## 4. PHY MMD map
| Addr | Size (B) | Field | Description / Contents | Hex |
|---|---|---|---|---|
| 96–127 | 32 | Vendor specific | Vendor Specific EEPROM | all 00 |
| 128–255 | 128 | Reserved | Reserved for SFF-8079 | all 00 |
Clause-45 MMDs behind the bridge:
**Field note:** the shipped FS unit deviates from these reference values where it is *more*
honest about being copper — Connector reads 22 (RJ45) not 21; Vendor Name reads "FS";
Vendor PN reads "SFP-10G-T-100"; Options read 00 1A. Critically, address 92 (Diagnostic
Monitoring Type) = 00 → **no A2h DOM is implemented** (the "optical DOM" some tools expect
is absent; only the PHY command handler exposes temperature/voltage/SNR).
## 2. SMI (I2C→MDIO) Communication Protocol for the SFP's PHY
The Copper SFP serial ID is at A0h. The physical IC (the PHY) is also accessible via 2-wire
bus at address **ACh** — the PHY address is `1010110x` where x is the R/W bit (0xAC write /
0xAD read).
- **PHY register write — one I2C frame:** after START, send 0xAC (PHY address), then
`000+DevAD` (device address of PHY), then Reg_H and Reg_L (register address), then Data_H
and Data_L, before STOP.
- **PHY register read — two I2C frames:** first frame sends 0xAC and `001+DevAD` with Reg_H,
Reg_L before STOP. Second frame sends 0xAD after START, then reads Data_H, Data_L before
STOP.
## 3. SMI Reading and Writing Time Sequence
**SMI Write register** (6 I2C bytes): `S [0xAC] [000+DevAD] [Reg_H] [Reg_L] [Data_H] [Data_L] P`
- 1st byte: 0xAC (8 bits)
- 2nd byte: 0b000 + DEVAD (5 bits)
- 3–4 bytes: Register Address (16 bits)
- 5–6 bytes: Write Data (16 bits)
**SMI Read register** (7 I2C bytes, two frames):
`S [0xAC] [001+DevAD] [Reg_H] [Reg_L] P` → **Delay > 1 mS** → `S [0xAD] [Data_H] [Data_L] P`
- 1st byte: 0xAC (8 bits)
- 2nd byte: 0b001 + DEVAD (5 bits)
- 3–4 bytes: Register Address (16 bits)
- **Delay > 1 mS (Important: for Host access Copper SFP PHY through I²C)**
- 5th byte: 0xAD (8 bits)
- 6–7 bytes: Read Data (16 bits)
**Bit-level examples** (colored waveform: Start / Master / Slave-ACK / Stop):
- *Write 0x55AA to DEVAD 1 Register 0xA820.*
- *Read 0x8542 from DEVAD 1 Register 0x0003* — note the final read data byte is **NAK**'d by
the master before STOP, and the `Delay > 1 mS` sits between the address frame and the data
read.
**Field note:** these diagrams are the authority for our `sff_i2c` framing — every written
byte is slave-ACKed, the final read byte is master-NAKed, and the >1 ms inter-frame delay is
mandatory (a single-byte read with no delay sees the bridge as inert/zero). Validated on
hardware; the compound `x` op holds the whole write→delay→read under one bus lock.
## 4. PHY Device Register Map Summary (Clause-45 MMDs)
| DEVAD | Block |
|---|---|
| 1 | 10GBASE-T PMA/PMD |
| 3 | 10GBASE-T PCS; XFI_M (XGMII) block also on DEVAD 3 |
| 7 | AN; SGMII block and 10/100/1000BASE-T PCS/PMA/PMD at 7.0xFFE0–0xFFFF |
| 30 | Top level (user-defined) |
| 1 | 10GBASE-T PMA/PMD (Clause 45 MMD) |
| 3 | 10GBASE-T PCS (Clause 45 MMD); XFI_M (XGMII) block is DEVAD 3\* |
| 7 | AN (Clause 45 MMD); SGMII (XGMII) and 10/100/1000BASE-T PCS/PMA/PMD at Clause-45 MMD 0xFFE0–0xFFFF |
| 30 | Top Level (User-Defined) (Clause 45 MMD) |
Side blocks: JTAG, SPI, BSC, PLL/clock, LED controller.
Side blocks (below the MMD bus): JTAG, SPI, BSC, PLL/Clock, LED Controller.
## 5. Reference access commands and 10G bring-up sequence
## 5. Accessing PHY Device Register Instructions
The ODM's host-side primitives are exactly our `sff_i2c` ops:
`Write_XGPHY_Register 0xAC [000+DEVAD] RegH RegL DataH DataL` and
`Read_XGPHY_Register 0xAC [001+DEVAD] RegH RegL, >1 ms, 0xAD DataH DataL`.
Two host command primitives implement PHY register read/write (command 1 = configuration,
command 2 = check XGPHY status):
Reference sequence "set PHY to work in 10GBE rate" (write in order):
- **Command 1 — `Write_XGPHY_Register p1 p2 p3 p4`:** p1 = 0xAC (8b); p2 = 0b000 + DEVAD (5b);
p3 = Register Address (16b, 2 bytes); p4 = Write Data (16b, 2 bytes).
- **Command 2 — `Read_XGPHY_Register p1 p2 p3 p4 p5 p6`:** p1 = 0xAC (8b); p2 = 0b001 + DEVAD
(5b); p3 = Register Address (16b); p4 = Delay > 1 mS (Important: for Host access Copper SFP
PHY through I2C); p5 = 0xAD (8b); p6 = Read Data (16b).
| Frame | Register = value | Meaning |
**Example — set PHY to work in 10GBE rate** (write these 8 frames one by one; the doc text
says "9 commands" but lists 8). The datasheet gives only the `Write_PHY_Register …` frames;
the `Register = value` column is a mechanical decode of the frame bytes, and the **Meaning
column is our annotation, not datasheet text**.
| Frame | Register = value | Meaning (our annotation) |
|---|---|---|
| AC 01 00 00 20 40 | 1.0 = 0x2040 | PMA control: 10G speed select |
| AC 01 00 07 00 09 | 1.7 = 0x0009 | PMA control 2: 10GBASE-T type |
| AC 07 00 10 10 01 | 7.16 = 0x1001 | AN advertisement |
| AC 07 00 20 10 03 | 7.32 = 0x1003 | 10GBASE-T AN control |
| AC 07 00 3C 00 08 | 7.60 = 0x0008 | **EEE advertisement — advertises 10GBASE-T EEE** |
| AC 07 00 40 00 00 | 7.64 = 0x0000 | |
| AC 07 80 00 00 10 | 7.0x8000 = 0x0010 | vendor AN register |
| AC 07 00 00 B2 00 | 7.0 = 0xB200 | AN control: enable + restart |
| `Write_PHY_Register AC 01 00 00 20 40` | 1.0x0000 = 0x2040 | PMA control: 10G speed select |
| `Write_PHY_Register AC 01 00 07 00 09` | 1.0x0007 = 0x0009 | PMA control 2: 10GBASE-T type |
| `Write_PHY_Register AC 07 00 10 10 01` | 7.0x0010 = 0x1001 | AN advertisement |
| `Write_PHY_Register AC 07 00 20 10 03` | 7.0x0020 = 0x1003 | 10GBASE-T AN control |
| `Write_PHY_Register AC 07 00 3C 00 08` | 7.0x003C = 0x0008 | EEE advertisement — advertises 10GBASE-T EEE |
| `Write_PHY_Register AC 07 00 40 00 00` | 7.0x0040 = 0x0000 | |
| `Write_PHY_Register AC 07 80 00 00 10` | 7.0x8000 = 0x0010 | vendor AN register |
| `Write_PHY_Register AC 07 00 00 B2 00` | 7.0x0000 = 0xB200 | AN control: enable + restart |
The EEE-advertisement line means the reference bring-up (and possibly the module
firmware's own defaults) leaves 10GBASE-T EEE negotiable — verify and disable
for measurement runs (see the probe results in README.md).
**Field note:** the EEE-advertisement line (7.0x003C = 0x0008) means the reference bring-up —
and possibly the module firmware's own defaults — leaves 10GBASE-T EEE negotiable. Verify and
force EEE/AutogrEEEn off for measurement runs (see the EEE-off recipe and probe results in
[README.md](README.md)).