Appendix: 40G Operation

MMA1L10-CR 100GbE QSFP28 LR4 Transceiver Product Specifications

This transceiver is SFF-8636 compliant. Its EEPROM contains advertisement bytes (bytes 193, 194 and 224) which contains information on its implemented features. These are read-only and cannot be changed by the host system.

The command registers are used to set programmable functions, i.e. they are writeable, but fall back to their default values when the transceiver is turned off/on. The command registers are bytes 98, 234-239 and have the functions listed below.

The transceiver comprises programmable input equalization in the transmit direction (to the fiber) as well as programmable equalization in the receive direction (from the fiber). Selectable retiming is implemented in all lanes in both transmit and receive direction and is enabled for 100G transmission by default.

Control of Equalizer, Emphasis and Retiming

Page 00 Byte

Bit

Description

Default

193

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2

Programmable Tx input equalizers implemented (1 = implemented)

1

1

Programmable Rx output emphasis implemented (1 = implemented)

1

0

Programmable Rx output Amplitude (1=implemented)

1

194 Advertisement

7

Tx CDR on/off control implemented (1 = implemented)

1

6

Rx CDR on/off control implemented (1 = implemented)

1

5

Tx CDR Loss-of-Lock (LOL) flag implemented (1 = implemented)

1

4

Rx CDR Loss-of-Lock (LOL) flag implemented (1 = implemented)

1

98

Retiming Control

7

Tx4 CDR control (1 = enabled)

1

6

Tx3 CDR control (1 = enabled)

1

5

Tx2 CDR control (1 = enabled)

1

4

Tx1 CDR control (1 = enabled)

1

3

Rx4 CDR control (1 = enabled)

1

2

Rx3 CDR control (1 = enabled)

1

1

Rx2 CDR control (1 = enabled)

1

0

Rx1 CDR control (1 = enabled)

1

Note: Set all CDR controls to 0 for 4 x 10 = 40 Gbps operation.

Page 03 Byte

Bit

Description

Default

224

Advertisement

7-4

Maximum Tx input equalization implemented

7

3-0

Maximum Rx output emphasis implemented

7

234

Control

7-4

Tx1 input Equalizer Control

4

3-0

Tx2 input Equalizer Control

4

235

Control

7-4

Tx3 input Equalizer Control

4

3-0

Tx4 input Equalizer Control

4

236

Control

7-4

Rx1 output Emphasis Control

2

3-0

Rx2 output Emphasis Control

2

237

Control

7-4

Rx3 output Emphasis Control

2

3-0

Rx4 output Emphasis Control

2

238

Control

7-4

Rx1 output Amplitude Control

7

3-0

Rx2 output Amplitude Control

7

239

Control

7-4

Rx3 output Amplitude Control

7

3-0

Rx4 output Amplitude Control

7

Note: Addresses are in decimal in accordance with the terminology used in SFF-8636.

NVIDIA switches and NICs automatically set both emphasis, amplitude, equalization, and retiming as part of the link-up procedure.

The transceiver’s compliance with the SFF-8636 standard allows it to be used in other systems, but the retiming may need to be configured manually and equalization and emphasis may need further optimization for best performance.

© Copyright 2023, NVIDIA. Last updated on May 22, 2023.