Technical data

Introducing the Product and Installing the Software
1.2 The STEP 7 Standard Package
Programming with STEP 7
Manual, 05/2010, A5E02789666-01 31
Diagnosing Hardware
These functions provide you with an overview of the status of the programmable controller. An
overview can display symbols to show whether every module has a fault or not. A double-click on
the faulty module displays detailed information about the fault. The scope of this information
depends on the individual module:
• Display general information about the module (for example, order number, version, name) and
the status of the module (for example, faulty)
• Display the module faults (for example, channel fault) for the central I/O and DP slaves
• Display messages from the diagnostic buffer
For CPUs the following additional information is displayed:
• Causes of faults in the processing of a user program
• Display the cycle duration (of the longest, shortest, and last cycle)
• MPI communication possibilities and load
• Display performance data (number of possible inputs/outputs, bit memory, counters, timers,
and blocks)
Programming Languages
The programming languages Ladder Logic, Statement List, and Function Block Diagram for S7-300
and S7-400 are an integral part of the standard package.
• Ladder Logic (or LAD) is a graphic representation of the STEP 7 programming language. Its
syntax for the instructions is similar to a relay ladder logic diagram: Ladder allows you to track
the power flow between power rails as it passes through various contacts, complex elements,
and output coils.
• Statement List (or STL) is a textual representation of the STEP 7 programming language,
similar to machine code. If a program is written in Statement List, the individual instructions
correspond to the steps with which the CPU executes the program. To make programming
easier, Statement List has been extended to include some high-level language constructions
(such as structured data access and block parameters).
• Function Block Diagram (FBD) is a graphic representation of the STEP 7 programming
language and uses the logic boxes familiar from Boolean algebra to represent the logic.
Complex functions (for example, math functions) can be represented directly in conjunction
with the logic boxes.
Other programming languages are available as optional packages.