Lenze Global Drive PLC Developer Studio - Manual (Page 9)

Drive PLC
Preface and general information
1−3
l
DrivePLC DE 6.0
1.2 System block introduction
For a long time, Lenze has followed the principle of describing controller functions with the aid of
function blocks (FBs). This principle can also be found in the IEC 61131−3 standard.
·
Functions which can be used as software functions in projects are stored in function libraries
as function blocks or functions.
·
In addition, quasi−hardware functions are available as system blocks (SBs).
1.2.1 System block principle
The system−block principle can be explained by means of a PLC system in a rack:
·
The rack contains the CPU, digital I/Os, analog I/Os, counter card, positioning card, etc. as
additional cards:
CPU x x x x x x
x = Additional cards
·
The CPU can directly access the additional cards and process the resulting information.
·
Additional cards have fixed addresses for access.
With Lenze PLC controllers, system blocks can be compared with these additional cards!
System blocks are special (hardware) function blocks permanently integrated into the
run−time system of the PLC.
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SBs can address real hardware.
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SBs are assigned/identified through so−called node numbers. ( ^ 1−4)
·
SB inputs and outputs are accessed via system variables or absolute memory addresses.
( ^ 1−5)
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Inputs/outputs are always classified from the program’s point of view. ( ^ 1−6)
·
Required SBs must be explicitly linked to the project via the control configuration of DDS.
(
^ 1−7)