ABB Advant Controller 450 User Manual

Advant
®
Controller 450 User’s Guide
Section 4.1.11 Data Transport
3BSE 002 415R701 Rev A 4-27
4.1.11.2 Reading-out Phase
The execution of all execution units is concluded with a reading-out phase. This means that
output data from the execution unit is obtained from the executions of all of the PC elements in
the unit.
The following example illustrates the requirements for reading-out elements. Assume two
execution units with the cycle times 500 ms and 50 ms, respectively, see Figure 4-19.
A value is calculated in the execution unit with the cycle time 500 ms and a limit check is
performed on the calculated value. These values (VALUE and VALUE
>
LIMIT) are connected
to an execution unit with cycle time 50 ms where the logical signal VALUE
>
LIMIT controls
an analog output with a fixed value MAX or with the calculated signal VALUE. Assume that
when element .10 has been executed (but not .11), an interrupt signal with the cycle time 50 ms
is received from the execution unit. The PC element in this unit works with the values of the
signals VALUE
>
LIMIT and VALUE, which are not associated with one another. To prevent
this, the system automatically introduces a reading-out element (an “invisible” PUT element).
The purpose of the reading-out element is to ensure that the output signals from an execution
unit only become legible for PC elements within other execution units when all PC elements
within the unit have been executed.
If output signals from an execution unit are to be stored in the data base, all data base points are
updated when all PC elements within the unit have been executed.
Figure 4-19. Example, Reading-out Phase
CONTRM
CONTRM
500ms
50ms
Execution unit 1
Execution unit 2
COMP
.10
.11
.2
ACT
max
Analog
output
Value > limit
Value
Limit

ABB Advant Controller 450 Specifications

General

Brand	ABB
Model	Advant Controller 450
Category	Controller
Language	English