FOUNDATION Fieldbus H1

Compact FF Link, redundant

Depending on operator preference, FOUNDATION Fieldbus (FF) H1 can be used in addition to PROFIBUS PA as the fieldbus for the direct connection of transmitters and actuators to the SIMATIC PCS 7 process control system.

Examples of FOUNDATION Fieldbus H1 architectures

When FOUNDATION Fieldbus H1 is integrated in the SIMATIC PCS 7 process control system, PROFIBUS DP acts as a link. The following graphical representations show possible FOUNDATION Fieldbus H1 architectures with:

• PROFIBUS DP master in non-redundant design (AS Single Station)
• PROFIBUS DP master in redundant design (AS redundancy station)

Depending on the configured PROFIBUS DP master, the gateway between PROFIBUS DP and FOUNDATION Fieldbus H1 is formed by a single Compact FF Link (AS single station) or a redundant Compact FF Link pair (AS redundancy station) (for details, see graphics). One FF fieldbus segment can be operated on each gateway.

FOUNDATION Fieldbus H1 on an AS Single Station as PROFIBUS DP master

FOUNDATION Fieldbus H1 on an AS redundancy station as PROFIBUS DP master

Line architecture with single Compact FF Link

A line segment can be connected to an individual PROFIBUS DP line via a Compact FF Link. The FF‑field devices can be integrated into the line segment via AFD active field distributors, e.g. AFD4, AFD4 RAILMOUNT, AFD4 FM and AFD8 (approval for Ex Zone 2/22) and AFDiSD (approval for Ex Zone 1/21). The FF‑field devices are connected to these field distributors using short-circuit-proof spur lines.

Alternatively, it is possible to operate up to 8 AFD field distributors, up to 5 AFDiSD field distributors or any combination of up to 5 AFDiSD and AFD field distributors in a line segment. The last field distributor at the end of the line farthest away from the Compact FF Link automatically activates its bus terminating resistor.

Ring architecture with redundant Compact FF Links

The highest availability can be achieved with a FOUNDATION Fieldbus H1 ring segment, which can be connected to a redundant PROFIBUS DP via a redundant Compact FF Link pair.

The FF field devices are integrated into the ring segment using the short-circuit-proof spur lines of the AFD or AFDiS active field distributors. The number of field distributors is limited as with the line architectures (up to 8 AFD, up to 5 AFDiS or any combination of up to 5 AFDiS and AFD).

The bus is terminated automatically and is immediately adapted in the event of changes or faults on the bus. An extension on the fieldbus or replacement of a Compact FF Link during operation is possible.

Properties of FOUNDATION Fieldbus H1

Like PROFIBUS PA, the FOUNDATION Fieldbus H1 is based on IEC 61158‑2. With MBP (Manchester coded Bus Powered) transmission system, digital data is transmitted and power is supplied to the bus nodes on a shielded two-wire cable. The constant transmission rate is 31.25 Kbps.

Up to 32 bus nodes (Compact FF Link + field devices) can be operated on one fieldbus segment (typically 8 to 12 devices). The field devices are integrated into the fieldbus segment via AFD (approval for Ex Zone 2/22) or AFDiS (approval for Ex Zone 1/21) active field distributors. Intrinsically-safe FF devices connected via AFDiS active field distributors can be installed in hazardous areas in accordance with Ex Zone 1/21 or 0/20.

The total length of the fieldbus segment is restricted to 1 900 m. If AFDs (active field distributors) are used, both the length of the spur lines for connecting devices and the quality of the cable used must also be considered when calculating the total length of the bus segment. Spur lines on the AFDiSD are not relevant to the total length of the bus segment.

The spur lines can have the following maximum lengths:

• Up to 120 m in accordance with IEC 61158‑2
• Up to 120 m in accordance with IEC 60079-27 (FISCO)

With AFD active field distributors, the maximum values are reduced if necessary, depending on the number of spur lines of the bus segment (for details, see the "Technical specifications" section). With AFDiSD active field distributors, this reduction is canceled by the integrated repeater function.

The SIMATIC Fieldbus Calculator provides help in calculating and designing fieldbus segments:
https://support.industry.siemens.com/cs/ww/en/view/53842953

The FOUNDATION Fieldbus H1 combines cyclic and acyclic communication. Time-critical tasks such as the transfer of process data are executed cyclically according to an exact processing schedule. On the other hand, non-time-critical information such as maintenance/diagnostics data or configuration data is transferred acyclically.

Device management with EDD

The field device data for the following block types are distributed according to the block model:

• Device block (device-specific information)
• Function block (implemented functions)
• Transmission block (function for controlling input/output variables of a function block)

Fieldbus Foundation provides pre-defined device descriptions (standard DD) for the basic functions of specific field device types. The basic functions of the devices (e.g. analog input, digital output, etc.) are implemented by means of various standard function and transmission blocks.

The device descriptions are interpreted with SIMATIC PDM.

Control in the field

Function and transmission blocks can also be interconnected to form control loops. Together with suitable field devices, such a control application operates independent of the controller (automation system) of the control system.

Characteristic features at a glance

• Bus power supply to the field devices
• Topology: Line, tree, ring
• Integration of intrinsically safe field devices in hazardous areas with barriers
• Deterministic time response
• Interoperability due to standardized bus interface and device integration with standardized device descriptions
• Support of "Control in the field"

Integration in SIMATIC PCS 7

The FOUNDATION Fieldbus H1 can be integrated seamlessly in the SIMATIC PCS 7 process control system using PROFIBUS DP as link. The gateway between PROFIBUS DP and FOUNDATION Fieldbus H1 is realized with Compact FF Links. Either a single Compact FF Link or a redundant pair is used based on the selected bus architecture (see "Design" section).

Engineering of the FOUNDATION Fieldbus H1 segments is implemented as for PROFIBUS PA. Diagnostic information and configured maintenance information for Compact FF Links and FF devices are available via the SIMATIC PCS 7 Maintenance Station. SIMATIC PCS 7 generates the diagnostics screens automatically.

System requirements

• System software SIMATIC PCS 7 V8.1+ SP1 or higher
• SIMATIC PDM V8.2+SP1 or higher with SIMATIC PDM Communication FOUNDATION Fieldbus