Topology

MBP: If MBP transmission technology is used, basically any topology is permissible. Linear and tree structures and combinations of both are thus possible. In practice, the “trunk & spur topology” has established itself as the de-facto standard, as it is especially clear and well-laid-out. Thanks to the technically-mature installation technologies available on the market, it also exhibits a high degree of robustness. The overall length of a segment may not exceed 1,900 m. Also, the maximum length for a spur in intrinsically-safe applications is 60 m.

Coupling RS485 and MBP Transmission Technology: The MBP transmission technology is typically limited to certain subsegments of a system, e.g. a group of field devices in a hazardous area. The connection of such subsegments to the RS485 segment is carried out using segment couplers or links.

• Segment couplers are transparent from the standpoint of the bus protocol, the devices of the MBP segment are directly visible on the DP side and the segment coupler itself does not require configuration.
• Links, on the other hand, are intelligent and map all devices connected in the MBP segment as a single slave in the RS485 segment. The link needs to be configured and restricts the total amount of data that can be transferred to and from the connected devices to 244 bytes. The cyclical data from the PA devices is compressed into a single DP telegram on the DP side and must be reselected by the DP master. The faster DP segment enables a number of PA segments to be integrated into a single DP network via segment couplers or links.