ABB Advant Controller 450, User Manual

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Advant
®
Controller 450 User’s Guide
Chapter 4 Runtime Operation
4-18 3BSE 002 415R701 Rev A
4.1.8.2 Process Communication
An Advant Controller 450 normally exchanges signals with a process via inputs and outputs.
Current data for these units is stored in the data base. Data consists of parameters for each board
such as board address. The PC program can read, for each channel on a board, information such
as the channel value, if there is any blocking of the data value, and so on. A PC program
normally utilizes the actual value of the signal.
Reading data in and out, between process and data base, is performed by the module for process
communication. For the most important types of input and output boards, this is performed in
accordance with the following:
DI:
Each digital input board (this applies to most types) monitors the channels for changes in
value. If there is any change, an interrupt signal is transmitted to the processor and the
kernel starts the program for reading in the new measured value for storage in the data
base.
Digital input boards can also be read cyclically. All channels on the board are then read
and the new values are stored in the data base.
AI:
Each channel on an analog input board is read cyclically. The cycle time, which can be set
individually, is stored in the data base. For temperature measurement boards (Pt100 and
thermocouple boards), the conversion is started cyclically. When the conversion is
completed, the board generates an interrupt. The inputs are handled so that the
measurement signal is filtered and converted to process-related units. The limits are
checked and then stored in the data base. The reading is normally performed synchronous
with the execution of PC modules with the same cycle time.
DO:
Each time an execution unit in a PC program is executed, the value at the output is stored
in the data base. If a change has occurred since the preceding execution, a read-out
program for read-out to the digital output board is started.
AO:
Analog outputs are processed in the same way as digital outputs. Process-related units
must first, however, be converted to digital values within the range of the D/A-convertor.
You can select either current or voltage with solder straps on the connection unit. In the
case of boards with expanded supervision (DSAX 110), the analog output value is read
back to permit a comparison with the database value.
4.1.8.3 Diagnostics for the System Program
When an engineering station is connected to an Advant Controller, you can analyze the reason
for the stoppage, the status of the internal communication channels, and so on. You can also use
the engineering station for fault-tracing in the application program. For a detailed description of
the different commands used for this purpose, see the reference manual AMPL Configuration
Advant Controller 400 Series.