Page 138 - Gefran - Inverter system and power supply unit (ADV200 Drive family)

138 Inverter System & Power Supply Unit

• Debug tools • Ladder Diagram (LD)
MDPlc integrates a series of di- The representation of logical se-
agnostic tools supporting the ap- quences in the form of the ladder
plication debug, its setting and diagram originates from the area
optimisation. MDPlc allows the of electrical plant engineering.
display, both numerically and LD is based on the methods
PROGRAMMAZIONE • Keypad, GF_eXpress, MDPlc, ...
ADV200 - 4 • Basic
graphically, and in suitable win- used to design relay logic. This
dows of all drive and application form of representation is particu-
variables which have been con- larly suitable for implementing
figured via the drag-and drop mode. The graphic curves are dis- relay switching operations in PLC programs.
played with different colours for clarity; the different colours can be
connected to configurable events and conditions (trigger). Because • Function Block Diagram (FBD)
the synchronous acquisitions are buffered at 1ms, the variables are The basic idea behind PLC pro-
used with high accuracy so as to give a precise analysis of their gramming with the function block
condition. diagram is that the program is
During the application development and testing, it is possible to in- structured in function-oriented
sert some triggers into pre-defined code points, which can be con- logical sequence cascades (net-
figured via a suitable window. The variables, which are read in a works). FBD derives from the
synchronous way with each trigger, can be displayed as numbers, graphic representation of flow
as diagrams or tables. The MDPlc environment supports the ap- diagrams, hence its ease of use.
plication debug by highlighting any programming errors, which are FBD is based on viewing a system in terms of the flow of signals,
then displayed in a suitable window during the compiling process. represented in the form of electronic circuit diagrams. Within one
The highlighted error is displayed together with its position and error network, the execution direction is always from left to right. All input
cause showing a direct link to the program section to be analysed. values must always be computed and available before the execu-
tion of a function block. The execution and evaluation of a network
• Instruction List (IL) is not completed until the output values of all elements have been
Instruction List is a low-level lan- calculated.
guage, with a structure similar to
a simple machine assembler lan- • Sequential Flow Chart (SFC)
guage. It is ideal for solving small Sequential Function Chart is a
straightforward problems where powerful graphical language for
there are few decision points and the description of the sequential
a limited number of changes in behaviour of a program in terms
the program execution flow. of states and transitions
IL can be used when the execution time is critical, for example in SFC describes the sequential as-
the MDPlc Fast Task at 1ms. pects of a program and it can be
used to divide a control problem
• Structured Text (ST) so that only relevant aspects to a specific phase are considered.
Structured text is a high-level SFC can be useful for the development of programs with a well-
language. It has a syntax that on defined "top-down" or "bottom-up" structure. Usually SFC can in-
first appearance is very similar to clude functions, function blocks and programs, and also actions
Pascal language. An ST pro- and transitions written with languages such as FBD, IL, LD or ST,
gram is usually organised as which are more suitable for descriptions of specific parts of the
continuous text. This is divided program and not of the sequential flow, implemented with the SFC
and structured into paragraphs, program.J
which represent the logic units of
the ST program.
The wide range of basic commands satisfies the needs of the data
management, computation functions, complex arithmetic calcula-
tions and control structure. ST has a comprehensive range of con-
structs to assign values to variables, to call functions and function
blocks, to create expressions, to evaluate conditions (IF, CASE)
and to implement iterations and loops (WHILE, REPEAT UNTIL).
ST is recommended in the MDPlc Fast Task at 1 ms, where the
execution time is critical.