SAFETY MANUAL - Tuv-fs.com
SAFETY MANUAL - Tuv-fs.com
SAFETY MANUAL - Tuv-fs.com
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<strong>SAFETY</strong> <strong>MANUAL</strong><br />
3.11.2 Language Selection<br />
The IEC1131 TOOLSET offers many programming tools to develop algorithms to<br />
meet the needs of virtually any real-time control application. The configuration and<br />
programming languages approved for use in SIL 3 or AK6 safety related application<br />
is shown in Table 7.<br />
Safety<br />
Related<br />
Function Block (FB)<br />
Instruction List (IL)<br />
Structured Text (ST)<br />
Ladder Diagrams (LD)<br />
Non-Safety<br />
Sequential Function Chart (SFC)<br />
‘C’<br />
Table 7 - Safety Related Programming Language<br />
• Safety Related Languages. For those languages that have been classified as<br />
‘safety related’. Commonly used functions have been exhaustively tested and<br />
may be used freely. Those included within the certification testing are shown in<br />
para. 5. Further functions may be used subject to <strong>com</strong>pletion of testing<br />
<strong>com</strong>mensurate with the level used for the <strong>com</strong>monly used functions.<br />
• Non-Safety. The languages that have been classified for non-safety related<br />
application only shall NOT be used within a safety-related system.<br />
IL and ST include program flow control functions; these functions shall be used with<br />
caution to ensure that infinite loop or omitted logic conditions do not result. Where<br />
these constructs are used, it is re<strong>com</strong>mended that full branch and data<br />
coverage tests be performed on these sections of program. It is<br />
re<strong>com</strong>mended that only Boolean conditions be used for these constructs to<br />
ensure that a feasible set of tests can be applied.<br />
Application programmer generated function blocks may be created either on a<br />
project specific or library basis. Where these functions are to be used for<br />
safety-related applications, they shall be subject to exhaustive testing,<br />
<strong>com</strong>mensurate with that used for the <strong>com</strong>monly used functions (see para.<br />
3.11.3). Once the function block has been subject to this level of testing it may be<br />
used as for <strong>com</strong>monly used functions.<br />
There is provision for the TMR system to support multiple programs within a<br />
project. A <strong>com</strong>plete project may be classified as safety or non-safety related. A<br />
safety-related project may use the safety programming languages; non-safety<br />
programming languages cannot be used. A project classified as non-safety may<br />
use any of the programming languages and the full instruction set but shall not be<br />
used to implement safety related functions. A checklist for the selection of<br />
programming languages is given in para. 4.2.2.<br />
Doc Number P8094<br />
Issue 14 September 2003 Page 59 of 67
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