Fisher ROC protocol module

Danetta Bramhall

The 3100/3150-ROC Communication Module was commissioned for development by Bill Perkins at Questar, an Engineering/System Intergration firm. ROC is a proprietary protocol used on the Fisher-Rosemount RTU. The RTU also has Modbus compatibility. Unlike Modbus, ROC is based on a point context. Questar needed to access certain data, mainly historical, that Modbus could not access. "The ProSoft 3100/3150-ROC module contains opcodes 180 and 181 of the ROC protocol, allowing the user to read and write data that cannot be accessed via Modbus," said Ken Hopwood, Developer for ProSoft Technology, Inc.