PLDM Protocol Support

Computers & Servers

Platform Level Data Model over MCTP

What is PLDM?

PLDM (Platform Level Data Model) is a DMTF specification that defines structured data formats and message commands for platform management functions transported over MCTP. PLDM covers sensor monitoring and events, firmware update, BIOS configuration, and Redfish Device Enablement (RDE). It provides the application-layer semantics that BMCs and managed devices use to exchange telemetry, perform firmware updates, and manage platform configuration. Engineers debugging server and data center platform management need PLDM decode to verify sensor readings, firmware update sequences, event handling, and configuration parameter exchanges between the BMC and managed components.

PLDM Quick Reference

type Packet-based
signals MCTP transport
features DMTF platform management data model

Acute Instruments Supporting PLDM

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How to Analyze PLDM with Acute Instruments

1

Connect your Acute logic analyzer to the MCTP transport interface carrying PLDM traffic.

2

Attach a ground lead to the target board's ground reference.

3

In the Acute software, select the PLDM protocol decoder and assign the transport signals to the correct input channels.

4

Configure the decoder for the MCTP transport binding and PLDM message type of interest.

5

Capture and view decoded PLDM messages showing command types, sensor readings, completion codes, and data payloads.

Frequently Asked Questions

What sample rate is required for PLDM analysis?
PLDM is an application-layer protocol carried over MCTP, so the sample rate requirement is determined by the underlying transport. For SMBus MCTP, 2-4 MHz is sufficient. For Ethernet MCTP, match the PHY interface speed requirements. PLDM messages themselves are relatively infrequent, but firmware update transfers can be sustained, requiring adequate capture depth.
Why is my PLDM firmware update failing mid-transfer?
PLDM firmware update uses a multi-step sequence: RequestUpdate, GetPackageData, PassComponentTable, UpdateComponent, and ActivateFirmware. A failure mid-transfer often indicates a timeout, transfer error, or component table mismatch. Capture the MCTP bus during the firmware update to decode PLDM messages and identify which command received an error completion code and at what point in the sequence the failure occurred.
How many channels are needed for PLDM analysis?
Channel requirements are the same as for the underlying MCTP transport. For SMBus: 2 channels. For Ethernet: 6-12 channels depending on the interface. PLDM adds no additional physical signals beyond what MCTP and its transport require.

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