HB-37350-810-01-50F-EN PSC1-C-10 Installation manual V2.1.docx Page 174 of 189
Version: 50F
12.3.6 Hardware and software design
The specifications from the hardware and software specification are implemented in the actual
system design.
The specifications for the components to be used and their circuitry from the hardware
specification are to be met as are the specifications for the fault exclusions. Both are to be
safeguarded using suitable means and are to be documented.
The specifications from the software specification are also to be followed and fully
implemented in the software.
In addition, the higher-level specifications for the software from safety-related programming
are to be observed. These include:
Modular and clearly structured layout of the program
Assignment of functions to the safety functions
Comprehensible depiction of the functions by means of:
Unambiguous identifiers
Comprehensible comments
Wide-ranging usage of tested functions / function blocks
Defensive programming
12.3.7 Check on the hardware design
On completion of the planning, the hardware design is to be checked for compliance with the
specifications from the hardware specification.
In addition, compliance with the specific safety level for each individual safety function is to be
checked by means of suitable analysis. The analytical methods are described in the applicable
standards (e.g. EN ISO 13849-1).
Circuit diagram analysis:
Compliance with the safety-related aspects of the specifications is to be checked based on the
circuit diagram and the parts list.
In particular, to be checked are:
The component connection circuitry as per specifications,
The dual-channel layout as far as specified
The freedom from interaction of parallel, redundant channels.
The usage of components as per specifications
The check is to be made by means of a traceable analysis.
12.3.7.1 Iterative check on the safety level achieved
The safely level achieved is to be determined based on the circuit layout (= architecture single-
channel / dual-channel / with or without diagnostics), the device characteristic data
(information from manufacturer or appropriate sources) and the diagnostic coverage
(information from manufacturer of PES or general sources). The appropriate methods are to
be found in the underlying safety standard.
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