| Hardware The S5 line comes in the 90U, | | | | packed into individual blocks. Segments - Within blocks, |
| 95U,101U,100U,115U, 135U, and 155U chassis styles.Higher | | | | fine structuring is possible by programming subtasks in |
| the number, the more sophisticated and more | | | | individual segments. Comments - Both a complete |
| expensive the system. Within each chassis style, | | | | program as well as individual blocks or segments and |
| several CPUs are available, with varying speed, | | | | individual statements can be directly provided with |
| memory, and capabilities. Some systems provide | | | | comments. Methods of representation STEP 5 |
| redundant CPU operation for ultra-high-reliability control, | | | | programs can be represented in three different ways: |
| as used in the pharmaceutical manufacturing, for | | | | Statement List (STL) - The program consists of a |
| example. Each chassis consists of a power supply, | | | | sequence of mnemonic codes of the commands |
| and a backplane with slots for the addition of various | | | | executed one after another by the PLC. Ladder |
| option boards. | | | | Diagram (LAD) - Graphical representation of the |
| Available options include serial and Ethernet | | | | automation task with symbols of the circuit diagram |
| communications, digital input and output cards, analog | | | | Function Block Diagram (FBD) - Graphical |
| signal processing boards, counter cards, and other | | | | representation of the automation task with symbols to |
| specialized interface and function modules. Software | | | | DIN 40700/ DIN 40719. Absolute or symbolic |
| The S5 product line is usually programmed with a PC | | | | designations can be used for operands with all three |
| based software programming tool called Step 5. Step | | | | methods of representation. In LAD and FBD complex |
| 5 is used for programming, testing, and commissioning, | | | | functions and function block calls can be entered via |
| and for documentation of programs for S5 PLCs. The | | | | function keys. They are displayed on the screen as |
| original Step 5 versions ran on the CPM operating | | | | graphical symbols. Blocks Five types of blocks are |
| system. | | | | available: Organization blocks (OB) - for managing the |
| Later versions ran on MS-DOS, and then versions of | | | | control program Programming blocks (PB) - contain the |
| Windows through Windows XP. The final version of | | | | control program structured according to functional or |
| Step 5 is version 7.2. No further development of this | | | | process-oriented characteristics Sequence blocks (SB) |
| product line has occurred since that time, due to its | | | | - for programming sequential controls Function blocks |
| announced obsolescence. In addition to Step5, Siemens | | | | (FB) - contain frequently occurring and particularly |
| offerred a proprietary State logic programming | | | | complex program parts Data blocks (DB) - for storing |
| package called Graph5. Graph5 is a sequential | | | | data required for processing the control program. |
| programming language intended for use on machines | | | | Some S5 PLCs also have block types FX (Extended |
| that normally run through a series of discrete steps. It | | | | Function Blocks), and DX(Extended Data Blocks); |
| simulates a State machine on the S5 platform. Several | | | | these are not distinct block types, but rather are |
| third-party programming environments have been | | | | another set of available blocks due to the CPU having |
| released for the S5. Most closely emulate Step5, | | | | more memory and addressing space. Operations |
| some adding macros and other minor enhancements, | | | | STEP 5 differentiates between three types of |
| others functioning drastically differently than Step5. | | | | operations: Basic operations, (e.g. linking, saving, loading |
| One allows Step5 programs to be cross-compiled to | | | | & transferring, counting, comparing, arithmetic |
| and from the C programming language and BASIC. | | | | operations, module operations) - These can be |
| Structured programming STEP 5 allows the creation | | | | performed in all three representations. Supplementary |
| of structured or unstructured programming, from simple | | | | operations and complex functions, (e.g. substitution |
| AND/OR operations up to complex subroutines. A | | | | statements, testing functions, word-by-word logic |
| STEP 5 program may, therefore, contain thousands of | | | | operations, decrement/increment and jump functions.) - |
| statements. | | | | These can only be executed in STL. System |
| To maintain maximum transparency, STEP 5 offers a | | | | operations (direct access the operating system) - |
| number of structuring facilities: Block technique - A | | | | These can only be executed in STL. |
| linear operation sequence is divided into sections and | | | | |