What are the Oil & Gas field device protocols?

The ROC (Remote Operations Controller) protocol is Emerson's proprietary protocol for its ROC300, ROC800, and Floboss S600+ series flow computers — the dominant product line in North American gas measurement. ROC organizes device data into a point type / logical number / parameter number addressing scheme. Every configurable item in the flow computer — a measurement input, a calculated variable, a configuration parameter, an archive record — is a point with a specific type number, a logical instance number, and a parameter offset.

Archive data is accessed through ROC's Archive Segment mechanism: the host requests a specific segment (hourly log, daily log, event log) for a given meter run, and the device responds with the records in that segment as a structured block. The protocol handles its own record sequencing and acknowledgment, making it much more reliable than Modbus for EFM archive retrieval over noisy serial links.

The Floboss S600+ uses the same underlying protocol family but with extensions for multi-run meter stations and more complex archive structures. TOP Server's ROC driver covers both ROC and Floboss variants, including the TCP-based ROC+ communication mode used by modern Emerson hardware.

Enron Modbus is an extension to standard Modbus that adds EFM-specific capabilities — primarily the ability to retrieve time-stamped historical records from flow computers. It was created by Enron Corporation in the 1990s as a way to standardize EFM data collection from multiple vendors using a single protocol, and was widely adopted across the industry even after Enron's demise.

The key additions over standard Modbus are: 32-bit floating point registers (Enron Modbus specifies how 32-bit floats are stored across two Modbus registers, with a defined byte order), 32-bit integer registers (again with a specified multi-register mapping), and critically, history record retrieval using Function Code 3 reads against a defined range of holding registers that map to historical archive entries, each containing a timestamp and a set of measured values.

The practical challenge with Enron Modbus is that the historical record structure — which registers map to which archive, what the timestamp format is, how many records a device stores — varies by vendor and even by device model. TOP Server's Enron Modbus driver handles the standard record retrieval pattern, and per-device configuration handles vendor-specific variations in record layout.

ABB's Totalflow protocol is used by the Totalflow XFC (eXtended Flow Controller) and XRC (eXtended Remote Controller) product line — a significant installed base in North American gas measurement, particularly in midstream gathering and transmission applications. The protocol is fully proprietary to ABB and is not interoperable with other vendors' equipment.

Totalflow uses an application-layer messaging scheme where the host sends command packets to request specific data types — current register values, periodic log records, event records, alarm records, and configuration data. Like ROC, the archive retrieval mechanism is designed specifically for EFM: records are retrieved by log type and time range, with the device returning structured record blocks containing timestamps and the measured/calculated values for each log period.

A distinguishing characteristic of Totalflow devices is their built-in Modbus server: in addition to the native Totalflow protocol, most XFC and XRC units can be configured to serve real-time values via Modbus holding registers. This gives SCADA systems a simple way to poll current values without the Totalflow driver — but the Modbus interface does not provide access to the historical archive records. For EFM data collection, the native Totalflow protocol is required.

Bristol BSAP (Bristol Standard Asynchronous Protocol) is the communication protocol for the Bristol Babcock product line of pipeline RTUs and remote controllers — the Network 3000 series and ControlWave family. Emerson acquired Bristol Babcock in 2004, and the product line continues as Emerson's pipeline SCADA solution, though it is separate from the ROC/Floboss product family.

BSAP is a peer-to-peer serial protocol designed for pipeline SCADA environments where multiple RTUs communicate with a central master over serial radio or leased line links. Bristol IP is the TCP/IP adaptation of BSAP — same application-layer protocol, carried over TCP rather than serial. The protocol addresses devices using a signal number / local station number scheme and supports reading and writing data sets (groups of related values) rather than individual registers.

ControlWave devices also support Modbus and OPC DA servers in addition to BSAP, but for full access to the device's historical archive, configuration data, and event logs, the native Bristol IP driver provides the most complete access. TOP Server's Bristol IP driver covers both serial BSAP and TCP-based Bristol IP communication modes.

Daniel Industries (acquired by Emerson) specializes in liquid flow measurement — crude oil, refined products, LNG, and custody transfer liquid metering. Daniel flow computers and the Floboss S600+ for liquid applications use a protocol family that is related to but distinct from the gas-focused ROC protocol. Daniel's own proprietary protocol and ROC-based communication are both used across the product range.

For pipeline operators running both gas and liquid measurement, having an OPC server that handles both ROC (for gas measurement) and Daniel (for liquid measurement) from a single platform simplifies the SCADA architecture significantly. TOP Server covers this with its Emerson suite of drivers spanning both gas and liquid measurement product families.