PLC Simulator
Modbus exception reference

Modbus Exception Code 02 — Illegal Data Address

The function is understood, but one or more requested data addresses are not mapped or allowed.

02
Load in Modbus sandbox

Exception meaning

Illegal Data Address

The function is understood, but one or more requested data addresses are not mapped or allowed.

Example exception response PDU

83 02

The exception response function is the original function with bit 7 set. For example, function 03 becomes 83. The second byte is the exception code.

Likely causes

  • 4xxxx reference notation was sent as the protocol offset
  • The request crosses an unmapped gap
  • The register exists only in a different model, firmware or operating mode

Evidence-based checks

  1. 1Translate the first documented reference into the correct zero- or one-based protocol offset
  2. 2Reduce quantity to one known register
  3. 3Confirm model, firmware and option-dependent map notes

Run the reference

Turn a protocol table into evidence.

Compose the request publicly, then use Pro for advanced graded exceptions, saved fixtures, complete history and project sharing.

Open sandbox
01 Read coils03 Read holding06 Write register