CIP PCCC: Troubleshooting the First Command Data Byte

Use the Wireshark field cip.pccc.cmd.code to inspect the first byte of PCCC Command Data. Apply an inequality display filter to isolate decoded values other than 0x10.

Map the Command Byte to the CIP PCCC Field

The CIP PCCC dissector exposes the first PCCC Command Data byte as cip.pccc.cmd.code. This field-level mapping avoids calculating a raw packet offset, provided Wireshark decodes the packet as CIP PCCC.

Filter Values That Do Not Equal 0x10

Open the capture and enter this expression in Wireshark's display-filter bar:

cip.pccc.cmd.code != 0x10

The displayed packets are those for which the decoded command-code field does not equal 0x10. Inspect each matching packet's CIP PCCC details to confirm the decoded field and packet context.

Verify That the Filter Applies to the Capture

1. Open the .pcapng log in Wireshark.
2. Select a packet expected to contain PCCC Command Data.
3. Expand its decoded CIP PCCC details and confirm that cip.pccc.cmd.code is present.
4. Apply cip.pccc.cmd.code != 0x10 and review the remaining packets.

If the field is absent, the supplied evidence does not establish whether the packet lacks PCCC Command Data or Wireshark did not decode it as CIP PCCC. Resolve that decoding question before interpreting an empty result.

Interpret the Result Without Assuming an Error

The filter proves only that a decoded command-code byte differs from 0x10. The evidence does not define the protocol meaning of other values or establish that every unequal value represents a slave-generated error. Correlate each match with the applicable device or protocol definition before classifying it as an error.

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