Signal Routing

hisl_0013: Usage of data store memory

ID: Title	hisl_0013: Usage of data store memory
Description	When using data store memory, set these data store memory model configuration parameters to error: Detect read before write Detect write after read Detect write after write Multitask data store Duplicate data store names
Notes	Use input and output signals instead of data store memory to communicate data whenever possible. Using data store memory blocks to communicate data across system boundaries can lead to unexpected results. If you have a Simulink® Design Verifier™ license, you can detect data store memory access violations in a model statically. Select the Design Verifier model configuration parameter Data store access violations. For more information, see Detect Data Store Access Violations in a Model (Simulink Design Verifier).
Rationale	Simulation diagnostics help identify places where data store memory communication invalidates the Simulink signal semantic.
Model Advisor Checks	Check safety-related diagnostic settings for data store memory (Simulink Check)
References	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 (1d) 'Use of defensive implementation techniques' Table 1 (1i) - 'Concurrency aspects' Table 3 (1i) 'Appropriate management of shared resources' EN 50128, Table A.4 (11) 'Language Subset' EN 50128, Table A.3 (1) 'Defensive Programming' DO-331, Section MB.6.3.3.b 'Software architecture is consistent’
Last Changed	R2024a
Examples

hisl_0015: Usage of Merge blocks

ID: Title	hisl_0015: Usage of Merge blocks
Description	To support unambiguous behavior from Merge blocks,
	A	Use Merge blocks only with conditionally executed subsystems.
	B	Specify execution of the conditionally executed subsystems such that only one subsystem executes during a time step.
	C	Clear block parameter Allow unequal port widths.
	D	Set the Outport block parameter Output when disabled to held for each conditionally executed subsystem being merged.
Notes	Simulink combines the inputs of the Merge block into a single output. The output value at any time is equal to the most recently computed output of the blocks that drive the Merge block. Therefore, the Merge block output is dependent upon the execution order of the input computations. To provide predictable behavior of the Merge block output, you must have mutual exclusion between the conditionally executed subsystems feeding a Merge block. Merge block parameter Allow unequal port widths is only available when configuration parameter Underspecified initialization detection is set to Classic.
Prerequisites	hisl_0303: Configuration Parameters > Diagnostics > Merge block hisl_0304: Configuration Parameters > Diagnostics > Model initialization
Rationale	A, B, C, D	Avoid ambiguous behavior.
Model Advisor Checks	Check usage of Merge blocks (Simulink Check)
References	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(b) 'Use of language subsets' ISO 26262-6, Table 1(d) 'Use of defensive implementation techniques' EN 50128, Table A.4 (11) 'Language Subset' EN 50128, Table A.3 (1) 'Defensive Programming' DO-331, Section MB.6.3.3.b 'Software architecture is consistent’
See Also	Merge block in the Simulink documentation
Last Changed	R2018b
Examples	Recommended
	Not Recommended

hisl_0021: Consistent vector indexing method

ID: Title	hisl_0021: Consistent vector indexing method
Description	Within a model, use:
	A	Consistent vector indexing method.
Rationale	A	Reduce the risk of introducing errors due to inconsistent indexing.
Model Advisor Checks	Check for inconsistent vector indexing methods (Simulink Check)
References	IEC 61508–3, Table A.3 (3) 'Language subset' IEC 61508–3, Table A.4 (5) 'Design and coding standards' IEC 62304, 5.5.3 - Software Unit acceptance criteria ISO 26262-6, Table 1 (1b) 'Use of language subsets' ISO 26262-6, Table 1 (1e) 'Use of well-trusted design principles' ISO 26262-6, Table 1 (1c) 'Enforcement of strong typing' ISO 26262-6, Table 1 (1f) 'Use of unambiguous graphical representation' ISO 26262-6, Table 1 (1g) 'Use of style guide' EN 50128, Table A.4 (11) 'Language Subset' EN 50128, Table A.12 (1) 'Coding Standard' DO-331, Section MB.6.3.2.b 'Low-level requirements are accurate and consistent'
Last Changed	R2024a

hisl_0022: Data type selection for index signals

ID: Title	hisl_0022: Data type selection for index signals
Description	For index signals, use:
	A	An integer or enumerated data type
	B	A data type that covers the range of indexed values.
	Blocks that use a signal index include: Assignment Index Vector Multiport Switch Selector Direct Lookup Table (n-D) 1-D Lookup Table 2-D Lookup Table n-D Lookup Table MATLAB Function Chart (Stateflow) Truth Table (Stateflow) Interpolation Using Prelookup
Rationale	A	Prevent unexpected results that can occur with rounding operations for floating-point data types.
	B	Enable access to data in a vector.
Model Advisor Checks	Check data types for blocks with index signals (Simulink Check)
References	IEC 61508–3, Table A.3 (2) 'Strongly typed programming language' 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' ISO 26262-6, Table 1 (1d) 'Use of defensive implementation techniques' EN 50128, Table A.4 (8) 'Strongly Typed Programming Language' EN 50128, Table A.3 (1) 'Defensive Programming' DO-331, Section MB.6.3.2.g – 'Algorithms are accurate' FLP30-C. Do not use floating-point variables as loop counters
See Also	Maximum Size Limits of Simulink Models
Last Changed	R2021b

hisl_0023: Verification of variant blocks

ID: Title	hisl_0023: Verification of variant blocks
Description	When verifying that a model is consistent with generated code, do the following:
	A	For each Variant block, set the Variant activation time to update diagram or update diagram analyze all choices.
Rationale	A	Simplify consistency testing between the model and generated code by restricting the code base to a single variant.
Model Advisor Checks	Check usage of variant blocks (Simulink Check)
References	DO-331, Section MB.6.3.3.b – Software architecture is consistent IEC 61508–3, Table A.4 (7) 'Use of trusted / verified software modules and components' ISO 26262-6, Table 1 (1e) 'Use of well-trusted design principles'
Last Changed	R2024a
See Also	Variant Subsystem

hisl_0034: Usage of Signal Routing blocks

ID: Title	hisl_0034: Usage of Signal Routing blocks
Description	When using Switch blocks, avoid comparisons using the ~= operator on floating-point data types.
Note	Due to floating-point precision issues, do not test floating-point expressions for inequality (~=). When the model contains a Switch block computing a relational operator with the ~= operator, 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 ~= operator within Switch blocks.
Rationale	Improve model robustness.
Model Advisor Checks	Check usage of Signal Routing blocks (Simulink Check)
References	DO-331, Sections MB.6.3.2.g 'Algorithms are accurate' IEC 61508-3, Table A.3 (3) – 'Language subset' 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' Table 1 (1d) - 'Use of defensive implementation techniques' EN 50128, Table A.4 (11) - 'Language Subset' Table A.3 (1) - 'Defensive Programming' MISRA C:2012, Dir 1.1
Last Changed	R2021a
Examples	Not Recommended Recommended