In short, the SRS should not include any design requirements.
However, this is a difficult discipline. For example, because of the
partitioning and the particular RTOS you are using, and the particular
hardware you are using, you may require that no task use more than 1 ms
of processing prior to releasing control back to the RTOS. Although
that may be a true requirement and it involves software and should be
tested – it is truly a design requirement and should be included in the
Software Design Document or in the Source code.
Consider the target audience for each specification to identify what goes into what documents.
Creates a product specification and gives it to Systems. It should define everything Systems needs to specify the product
Creates a System Specification and gives it to Systems/Software and Mechanical and Electrical Design.
Creates a Software Specification and gives it to Software. It should define everything Software needs to develop the software.
Thus, the SRS should define everything explicitly or (preferably) by
reference that software needs to develop the software. References
should include the version number of the target document. Also,
consider using master document tools which allow you to include other
documents and easily access the full requirements.