Communication Front-Ends - ABB MicroSCADA Pro SYS 600 Technical Description

SYS 600 *9.0
4.3.
36
MicroSCADA Pro
System Overview
Technical Description
Fig. 4.2.-3 Example of a COM 500 system
COM 500 sees each NCC and each local process unit as a station. (The local process
unit is a system object type.) The communication mainly passes through the process
database.
Communication from COM 500 to the Network Control Center (NCC) is based on
command procedures. The command procedures send information to the NET unit
for protocol conversion and transmission. Typically one command procedure is
needed for each type of data to be transferred. At start-up and after communication
disturbances all specified data is transferred. When the system is running, process
events generally activate the command procedures via event channels.
Commands and setpoints from the NCC to the substation are brought into the COM
500 application via process objects. The process objects activate, via event channels,
command procedures, which contain actual control commands to the process units.
Safety is increased by using select-before-execute commands and a two-step
authority check mechanism.

Communication front-ends

A communication front-end is a computer which is especially reserved for process
communication. It is connected to a base system through LAN. The communication
front-end is used for increasing the number of communication lines. It can also be
used for distributing the communication lines over LAN and to decrease the load of
the SYS 500 computer.
A communication front-end can contain either PC-NET or DCP-NET units. Usually
a communication front-end is equipped with a display and other operator
workstations facilities. An example of components in a communication front-end is
shown in Figure 4.3.-2. Components that can be found in a communication front-end
are DCP-NET software, a DCP card, COM ports and MFL.
1MRS751852-MUM
Standalone_COM