ProSoft Technology PS-QS-1x10-0781 - Manual (Page 8)

FieldServer Configuration Manual Page 8 of 90
FieldServer Technologies 1991 Tarob Court Milpitas, California 95035 USA Web: www.fieldserver.com
Tel: (408) 262-2299 Fax: (408) 262-2269 Toll Free: (888) 509-1970 email: [email protected]
2 OVERALL OPERATION PHILOSOPHY
The FieldServer functions as a bridge between two or more different Nodes (see Figure II). The information is
gathered by the Client side of the FieldServer from the Server Nodes via a Serial Port, Ethernet port or plug-in card.
Nodes may use different protocols and even different communication busses. The Client Node Descriptors contain
information about each Node including connection ports and protocol. Each Node is given a Node_Name and a
Node_ID. The data from a Server Node is stored on the FieldServer in a Data Array. The exact location as well as
the format of the information is determined by the Map Descriptors. The FieldServer can contain any number of
Data Arrays, but each Data Array can only store data in one format. The Client Map Descriptors describe where
the information is to be stored on the FieldServer, and the Server Map Descriptors describe how this information is
able to be accessed by a Client Node. On the Server side of the FieldServer, virtual Nodes are created to convert
the information stored in the Data Arrays to the format required by the Client Node. These Nodes can be accessed
by any of the available ports on the FieldServer at any time. The FieldServer thus acts as a Client and a Server
simultaneously.
Figure II - FieldServer Operation Theory
Example:
Consider a Modbus PLC with a set of 10 high alarms in address 00001 to 00010.
A Map Descriptor is allocated to fetch Data Objects from Modbus address 00001 length 10 and save this data to a
Data Array named PLC1, offset 20. The high alarm for sensor number 5 on PLC1 is thus stored in Data Array PLC1;
offset 24 (the fifth location starting at offset 20).
A DCS using Allen Bradley DH+ protocol can be configured to access the FieldServer and read the Data Array. The
FieldServer will appear to the DCS as another DH+ PLC. If the Virtual Node PLC1 is configured to contain the data
on sensor 5/PLC1 as a DH+ address B3:57, then the data needed for address B3:57 will be retrieved from Data
Array PLC1, offset 24.
Modbus
Dat a Hi ghway Pl us
Bridge
Data Arrays
Client Map Descriptors
Client Node Descriptors
Server Map Descriptors
Virtual Server Nodes
Location
Client
Side
Server
Side
Server Node
Client Node