30 September 2004
Modbus protocol becomes IEC PAS
The International Electrotechnical Commission (IEC) accepted the Modbus protocol, Modbus-IDA, as a publicly available specification (PAS).
The transmission control protocol (TCP) variant of the protocol, along with a companion protocol known as RTPS, were submitted to IEC SC65C as a real-time industrial Ethernet suite. The submission was possible by the recent granting of a type D liaison status to Modbus-IDA by the IEC. Of 25 countries voting on the proposal, there was only one negative vote. At the same time, the subcommittee accepted the specification as a new work item.
In approving the document, several national committees asked for a reformatting of the specification to allow for better integration into the revision of IEC-61158, the fieldbus standard. Modbus-IDA president Ken Crater said they intend to make this reformatting a priority for the organization.
Ownership of the Modbus protocol transferred last April from Schneider Automation to the independent nonprofit organization Modbus-IDA.
For related information, go to www.isa.org/networks.