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How Can I Best Capture MDIO Bus Transactions with Total Phase Tools?
Rena Ayeras

Question from the Customer:

I need a protocol analyzer to capture MDIO bus transactions. I have a Total Phase 10-Pin Grabber Split Cable on hand, but I don’t see any markings for MDC and MDIO signals. Which pins should I use, and which Beagle protocol analyzer do you recommend?

Response from Technical Support:

Thanks for your questions! For your use, we recommend the Beagle I2C/SPI Protocol Analyzer and Data Center Software version 2.20. Used together, they can easily display and capture MDIO bus transactions.

Beagle I2C/SPI Protocol Analyzer Data Center Software


About the Beagle I2C/SPI analyzer MDIO support:

  • Non-intrusively monitors MDIO up to 2.5 MHz
  • Monitors clause 22 and clause 45 MDIO
  • Pin 8 is the bidirectional management data input/output (MDIO signal), which is used to transfer data between the STA and the MMD.
  • Pin 7, is the management data clock (MDC signal), which is a control line that is driven by the STA and synchronizes the flow of the data on the MDIO line.

To capture MDIO signals, the sampling rate must be set properly: the minimum requirement for the sampling rate is twice the bus bit rate. To customize a program for your setup requirements, we recommend using Beagle Software API. Functional examples are provided, which you can use as-is or modify as needed.

The Beagle I2C/SPI analyzer signal level is 3.3V.  If you need to monitor a lower voltage MDIO bus, you can use the Level Shifter Board.

For additional information, please refer to the knowledge base article MDIO Background and the following sections of the Beagle Protocol Analyzer User Manual:

  • MDIO Background
  • Beagle I2C/SPI/MDIO Protocol Analyzer

We hope this answers your questions. Additional resources that you may find helpful include the following

More questions? You can also contact us and request a demo that applies to your application, as well as ask questions about the Beagle  protocol analyzers and other Total Phase products.

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