The Fieldbus Foundation has released an updated version of its FOUNDATION for Safety Instrumented Functions (SIF) technical specifications. The specifications now include support for FOUNDATION fieldbus H1 (31.25 bit/s) dual-mode devices employing field diagnostics capabilities, which are intended to simplify the process of developing field instrumentation employing the SIF protocol.
The Fieldbus Foundation says FOUNDATION for SIF has the potential to greatly improve plant and process safety through advanced diagnostics at both the device and network level.
The FOUNDATION for Safety Instrumented Functions protocol was approved by TÜV Anlagentechnik GmbH to meet the requirements of IEC 61508 up to, and including, Safety Integrity Level (SIL) 3.
With the dual-mode H1 device capability, instrumentation manufacturers can bring new safety products to market without having to design two entirely different devices. Developers can implement H1 devices with SIF features activated or de-activated. The Fieldbus Foundation says this means that plants will only have to stock one type of device that can be used as either a process device or a safety device.
When SIF mode is selected, the device will behave as specified by the SIF specifications; otherwise, it will function as a normal H1 instrument. To ensure conformance to safety standards, the two modes cannot run concurrently in the same device.
The latest FOUNDATION for SIF specification includes a number of updates to the System Architecture, Application Model, Protocol, Function Block and Device ITK Profile specifications to make this all possible. It also includes a new application note on macro cycle calculation.