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4-2. LC Programming Approach
U3-1021
4-2
2/99
Westinghouse Proprietary Class 2C
4-2. LC Programming Approach
In a typical LC application, information is sent from a field device to the LC’s J2
Application serial port to be transferred to the Controller. Data or commands from
the Controller may also be obtained by the LC and transmitted to the field device.
To implement an LC application, the following general steps are required:
•
Define the format of the data to be received (or transmitted) through the J2
serial port.
•
Create an LC application program to convert the data to an appropriate format and
place it in OIOB-accessible dual port RAM (or read data placed in dual port RAM
by the OIOB).
•
Create the Controller application program to place the OIOB information into
Ovation process points (or write point data to the OIOB).
Figure 4-1 illustrates the information flow between a field device and a Controller,
using the LC interface. In this example, data is transmitted to the LC from a field
device in RS-232 format. This data is made available to the Controller through the
OIOB.
Figure 4-1. Example LC Application
Controller
Processor
LC/J2
OIOB
Controller application must include
required process points and control
algorithms.
Field Device
RS-232 link
LC application program must perform
the following functions:
•
Convert RS-232 data to applicable
format for OIOB.
•
Write data to dual port static RAM for
OIOB access.