Foundation Fieldbus H1 is one of the FOUNDATION fieldbus protocol versions. Foundation H1 (31.25 kbit/s) is a bi-directional communications protocol used for communications among field devices and to the control system. It utilizes either twisted pair, or fiber media to communicate between multiple nodes (devices) and the controller. The controller requires only one communication point to communicate with up to 32 nodes, this is a significant improvement over the standard 4–20 mA communication method, which requires a separate connection point for each communication device on the controller system.

The Foundation Fieldbus H1 has support for Intrinsically Safe Wiring. Unlike other protocols, FOUNDATION H1 provides explicit synchronization of control and communication for precisely periodic (isochronous) communication and execution of control functions with minimized dead time and jitter. It synchronizes clocks in fieldbus devices for support of Function Block scheduling and alarm time-stamping at the point of detection.

The original concept was to connect as many fields devices as possible on controller field connection, limited only by signal strength.

Foundation HSE is a control network technology specifically designed for process automation to connect higher-level devices such as controllers and remote-I/O, high-density data generators etc., and for horizontal integration of subsystems.

Foundation HSE is based on unmodified IEEE 802.3 Ethernet and, therefore, is compatible with standard Ethernet equipment. FOUNDATION HSE provides complete "DCS style" redundancy with redundant network switches, redundant devices, and redundant communication ports ensuring unsurpassed availability. Foundation HSE is also based on standard IP, enabling it to coexist with other devices and ensuring compatibility with standard tools. At the highest level, Foundation HSE includes a standard application layer that provides interoperability between devices beyond the mere coexistence provided by Ethernet and TCP/IP. Foundation HSE communication is schedule-driven to minimize dead-time and jitter with support for peer-to-peer communication directly between devices. Again, a rigorous interoperability testing program ensures quality connectivity.

The hub-and-spoke tree topology of Ethernet makes it very easy to add and remove devices without upsetting the operating network. Because Foundation HSE is based on unmodified Ethernet, standard Ethernet tools can be used for installation qualification, testing, and troubleshooting. These tools speed up the resolution of communication problems. Foundation HSE is supported by better troubleshooting tools not available for RS485 and coax. Since Foundation HSE is based on UDP and TCP, standard network management tools employing SNMP, RMON, etc., can be used. Similarly, familiar IP addressing is used including support for DHCP.

The communication line can stretch 1900 meters without repeaters or 9500 meters with up to four allowed repeaters.

The communication methods supported are: