Specifications

8
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Chapter 8
General programming notes
This chapter provides information on the program (PLC ladder language),
address, and interface structures of the STEP7. The STEP7 uses a program
structure compatible with the IEC 1131-3 international standard. The program
structure allows ladder diagram programming that supports various languages
such as LAD, FBD, STL, and GRAPH. Thanks to the structured nature and
advanced features, programs are not only easy to understand, but far more
powerful than the conventional ladder logic. The PLC for the YS 840DI sys-
tem is the S7-300, allowing the use of LAD, FBD, and STL in ladder logic
design.
8.1 LAD/FBD/STL compatibility - - - - - - - - - - - - - - - - - - - - - - - - 8-2
8.2 Program structure - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-3
8.3 Address structure - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-4
8.3.1 Address symbols - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-4
8.3.2 Bit address - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-4
8.3.3 Addressing of input, output, bit memory, and data bits- - - - - - - - - - - - 8-5
8.3.4 Addressing of timers and counters - - - - - - - - - - - - - - - - - - - - - - - - - 8-5
8.4 Interface structure - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-6
8.4.1 General - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-6
8.4.2 Signals through the PLC/NC interface - - - - - - - - - - - - - - - - - - - - - - - 8-6
8.4.3 Data blocks- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-7
8.4.4 Program components- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-8