SmartVID Debug Checklist and Voltage Regulator Guidelines

ID 757318
Date 4/01/2024
Public

1.6. Example: How to Decode the PMBus Transaction Log

In this example, the Intel Agilex® 7 device operates as the PMBus master and the ISL68137 voltage regulator operates as slave with address = 0x60h and direct data format with coefficient m = 1, b = 0, and R = 0.

To decode the PMBus transaction log, follow these steps:

  1. Decode the transaction log from the protocol analyzer.
    1. The PMBus master sends VOUT_COMMAND(0x21h) to set slave (address = 0x60h) output voltage to 850 mV (0x0352h).
      Figure 4. PMBus Master sends VOUT_COMMAND
    2. The PMBus master sends READ_VOUT(0x8Bh) to request slave (address = 0x60h) to return the actual measured output voltage value. The PMBus slave responded to the request and return with the actual measured output voltage value, 847 mV (0x034Bh).
      Figure 5. PMBus Master sends READ_VOUT
  2. Decode the transaction log from the oscilloscope screenshot.
    Figure 6. Oscilloscope Transaction Log
    1. The PMBus master sends the VOUT_COMMAND(0x21h) to set slave (address = 0x60h) output voltage to 850 mV (0x0352h).
      Figure 7. PMBus Master sends VOUT_COMMAND
    2. The PMBus master sends READ_VOUT(0x8Bh) to request slave (address = 0x60h) to return the actual measured output voltage value. The PMBus slave responded to the request and return with the actual measured output voltage value, 847 mV (0x034Bh).
      Figure 8. PMBus Master sends READ_VOUT