Documentation

Logic and Bit Operations

hisl_0016: Usage of blocks that compute relational operators

ID: Title	hisl_0016: Usage of blocks that compute relational operators
Description	To support the robustness of the operations, when using blocks that compute relational operators, including Relational Operator, Compare To Constant, Compare To Zero, Detect Change, and If blocks:
Description	A	Avoid comparisons using the `==` or `~=` operator on floating-point data types.
Notes	Due to floating-point precision issues, do not test floating-point expressions for equality (`==`) or inequality (`~=`). When the model contains a block computing a relational operator with the `==` or `~=` operators, the inputs to the block must not be single, double, or any custom storage class that is a floating-point type. Change the data type of the input signals, or rework the model to eliminate using the `==` or `~=` operators within blocks that compute relational operators.
Rationale	A	Improve model robustness.
Model Advisor Checks	Check for Relational Operator blocks that equate floating-point types (Simulink Check)
References	IEC 61508-3, Table A.3 (2) 'Strongly typed programming language’ IEC 61508-3, Table A.3 (3) 'Language subset’ IEC 61508-3, Table A.4 (3) 'Defensive programming' IEC 62304, 5.5.3 - Software Unit acceptance criteria ISO 26262-6, Table 1 (1b) 'Use of language subsets' ISO 26262-6, Table 1 (1c) 'Enforcement of strong typing' EN 50128, Table A.4 (11) 'Language Subset' EN 50128, Table A.4 (8) 'Strongly Typed Programming Language' EN 50128, Table A.3 (1) 'Defensive Programming' DO-331, Section MB.6.3.1.g 'Algorithms are accurate' DO-331, Section MB.6.3.2.g 'Algorithms are accurate' MISRA C:2012, Dir 1.1
See Also	hisl_0017: Usage of blocks that compute relational operators (2)
Last Changed	R2018a
Examples	Positive Pattern: To test whether two floating-point variables or expressions are equal, compare the difference of the two variables against a threshold that takes into account the floating-point relative accuracy (`eps`) and the magnitude of the numbers. The following pattern shows how to test two double-precision input signals, `In1` and `In2`, for equality.

hisl_0017: Usage of blocks that compute relational operators (2)

ID: Title	hisl_0017: Usage of blocks that compute relational operators (2)
Description	To support unambiguous behavior in the generated code, when using blocks that compute relational operators, including Relational Operator, Compare To Constant, Compare to Zero, and Detect Change
	A	Set block parameter Output data type to `Boolean`.
	B	For Relational Operator blocks, verify that input signals are of the same data type.
Rationale	A, B	Support generation of code that produces unambiguous behavior.
Model Advisor Checks	Check usage of Relational Operator blocks (Simulink Check)
References	IEC 61508-3, Table A.3 (2) 'Strongly typed programming language’ IEC 61508-3, Table A.3 (3) 'Language subset’ IEC 61508-3, Table A.4 (3) 'Defensive programming' IEC 62304, 5.5.3 - Software Unit acceptance criteria ISO 26262-6, Table 1 (1b) 'Use of language subsets' ISO 26262-6, Table 1 (1c) 'Enforcement of strong typing' EN 50128, Table A.4 (11) 'Language Subset' EN 50128, Table A.4 (8) 'Strongly Typed Programming Language' EN 50128, Table A.3 (1) 'Defensive Programming' DO-331, Section MB.6.3.1.g 'Algorithms are accurate' DO-331, Section MB.6.3.2.g 'Algorithms are accurate' MISRA C:2012, Rule 10.1
See Also	hisl_0016: Usage of blocks that compute relational operators
Last Changed	R2018a

hisl_0018: Usage of Logical Operator block

ID: Title	hisl_0018: Usage of Logical Operator block
Description	To support unambiguous behavior of generated code, when using the Logical Operator block,
	A	Set block parameter Output data type to `Boolean`.
	B	Ensure input signals are of type `Boolean`.
Prerequisites	hisl_0045: Configuration Parameters > Math and Data Types > Implement logic signals as Boolean data (vs. double)
Rationale	A, B	Avoid ambiguous behavior of generated code.
Model Advisor Checks	Check usage of Logical Operator blocks (Simulink Check)
References	DO-331, Section MB.6.3.1.e—High-level requirements conform to standards DO-331, Section MB.6.3.2.e—Low-level requirements conform to standards DO-331, Section MB.6.3.1.g 'Algorithms are accurate' DO-331, Section MB.6.3.2.g 'Algorithms are accurate' DO-331, Section MB.6.3.4.e—Source code is traceable to low-level requirements. DO-331, Section MB.6.3.3.b—Software architecture is consistent. IEC 61508-3, Table A.3 (2) 'Strongly typed programming language’ IEC 61508-3, Table A.3 (3) 'Language subset’ IEC 61508-3, Table A.4 (3) 'Defensive programming' IEC 62304, 5.5.3 - Software Unit acceptance criteria ISO 26262-6, Table 1 (1b) 'Use of language subsets' ISO 26262-6, Table 1 (1c) 'Enforcement of strong typing' EN 50128, Table A.4 (11) 'Language Subset' EN 50128, Table A.4 (8) 'Strongly Typed Programming Language' EN 50128, Table A.3 (1) 'Defensive Programming' MISRA C:2012, Directive 10.1
Last Changed	R2017b

hisl_0019: Usage of bitwise operations

ID: Title	hisl_0019: Usage of bitwise operations
Description	To support unambiguous behavior, when using bitwise operations in Simulink blocks,
Description	A	Avoid signed data types as input to the block.
Notes	Bitwise operations on signed data types are not meaningful. If a shift operation moves a signed bit into a numeric bit, or a numeric bit into a signed bit, unpredictable and unwanted behavior can result. Bitwise blocks include: Bit Clear Bit Set Bitwise Operator Extract Bits Shift Arithmetic
Rationale	A	Support unambiguous behavior of generated code.
Model Advisor Checks	Check usage of bit operation blocks (Simulink Check)
References	DO-331, Section MB.6.3.1.g 'Algorithms are accurate' DO-331, Section MB.6.3.2.g 'Algorithms are accurate' IEC 61508-3, Table A.3 (3) 'Language subset’ IEC 61508-3, Table A.3 (2) 'Strongly typed programming language’ IEC 62304, 5.5.3 - Software Unit acceptance criteria ISO 26262-6, Table 1 (1b) 'Use of language subsets' ISO 26262-6, Table 1 (1c) 'Enforcement of strong typing' ISO 26262-6, Table 1 (1d) 'Use of defensive implementation techniques' EN 50128, Table A.4 (11) 'Language Subset' EN 50128, Table A.3 (1) 'Defensive Programming' EN 50128, Table A.4 (8) 'Strongly Typed Programming Language' MISRA C:2012, Rule 10.1
See Also	hisf_0003: Usage of bitwise operations
Last Changed	R2019a

Simulink Documentation

Support