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The SFP28 pin assignment is SFF-8419 compliant. 

SFP28 Function Definition

PinConnector Pin NamePort A Signal Name

1

VeeT

Module Transmitter Ground

2

Tx_Fault

Module Transmitter Fault

3

Tx_Disable

Transmitter Disable. Turns off transmitter laser output

4

SDA

2-wire Serial Interface Data Line

5

SCL

2-wire Serial Interface Clock

6

Mod_ABS

Module Absent. Grounded within the module

7

RS0

Rate Select 0, optionally controls SFP+ module receiver

8

Rx_LOS

Receiver Loss of Signal Indication

9

RS1

Rate Select 1, optionally controls SFP+ module transmitter

10

VeeR

Module Receiver Ground

11

VeeR

Module Receiver Ground

12

RD-

Receiver Inverted Data Output

13

RD+

Receiver Non-Inverted Data Output

14

VeeR

Module Receiver Ground

15

VccR

Module Receiver Power Supply

16

VccT

Module Transmitter Power Supply

17

VeeT

Module Transmitter Ground

18

TD+

Transmitter Non-Inverted Data Input. AC coupled

19

TD-

Transmitter Inverted Data Input. AC coupled

20

VeeT

Module Transmitter Ground

 SFP28 Module Pad Layout

Digital Diagnostic Monitoring Features

The transceiver’s management functions comply with SFF-8472.

  • Physical layer link tuning
    • Tx input equalization programmable in 11 levels up to 10 dB
    • Rx output pre-emphasis programmable in 8 levels up to 7 dB
    • Tx/Rx CDR control, refer to ‎Appendix
  • DDM – Readout and Warning/Alarm Indication
    • Rx receive optical power monitor
    • Tx transmit optical power monitor
    • Tx bias current monitor
    • Module supply voltage monitor
    • Module case temperature monitor
  • MSA supported features and interrupt indications
    • Tx & Rx LOS
    • Tx & Rx LoL
    • Tx fault
    • Tx & Rx disable