FOUNDATION Fieldbus Physical Media Connectivity
FOUNDATION fieldbus General Specifications
FOUNDATION Fieldbus is a Communication Protocol and physical method to interconnect smart devices such as temperature transmitters, pressure transmitters and valve actuators. The physical layer conforms to ISA SP50.02 and IEC 1158-2 standards for fieldbuses.
Fieldbus technology allows many smart devices to share one communication medium. The digital communication signal is superimposed onto a DC carrier. This reduces the amount of terminations to connect all the field devices to a host system and allows greater flexibility for future additions of I/O points.
A FOUNDATION fieldbus device is addressable and can store and transmit data. The devices can store values, track changes and use pre-set alarms to trigger. Based on pre-defined tag names, host systems can read transmitter values such as temperature and pressure to set values of a valve actuator.
Digital signal encoding is done using Manchester BiPhase-L and error checking is done with the CRC method. FOUNDATION fieldbus has two types of devices - A Basic Device (BD) which reads inputs, track values and set outputs if programmed to do so, and a Link Active Scheduler (LAS) which performs the same features as a BD and handles network communication timing between all the active devices on the network.