Glossary · Distributed automation and IEC 61499
Service interface function block (SIFB)
Also known as: SIFB, Service interface FB
German: Dienstschnittstellen-Funktionsbaustein
In IEC 61499, a service interface function block (SIFB) is a function block type that provides access to services of its resource or device, such as I/O, communication or timing, and whose behavior is specified by service sequences rather than by an ECC or internal network.
- IEC 61499
- Standards
In one sentence
An IEC 61499 service interface function block gives an application access to I/O, communication or timing services of a device.
Example
A PUBLISH block sends data to other devices and a SUBSCRIBE block receives it; an IX block reads a digital input of the local device.
How it applies
- Engineering: SIFBs connect the hardware-independent application to the real world. Communication SIFBs (such as publish/subscribe and client/server) realize connections between devices; I/O SIFBs access sensors and actuators. Their implementation is device-specific, while their interface is standardized or defined by a profile.
- Portability: Applications become device-specific where they use SIFBs. Keeping SIFBs at the edges of the application makes remapping easier.
- Testing: Service behavior, including error cases such as communication loss, must be tested on the target device, because it depends on the implementation.
- Documentation: Document each SIFB type with its service sequences, parameters (such as addresses or channels) and error behavior. Device documentation should list the SIFBs a device supports.
SIFB vs. basic function block
A Basic function block describes its behavior with an ECC and algorithms. An SIFB describes its behavior from the outside with Service sequence diagrams, because the implementation lies in the device.