Memory Requirements
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Introduction
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Memory is typically a limited resource in real-time embedded systems, therefore, RTEMS can be configured  to utilize the minimum amount of memory while meeting all of the applications requirements.  Worksheets are provided which allow the RTEMS application developer to determine the amount of RTEMS code and RAM workspace which is required by the particular configuration.  Also provided are the minimum code space, maximum code space,  and the constant data space required by RTEMS.

Data Space Requirements
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RTEMS requires a small amount of memory for its private variables.  This data area must be in RAM and is separate from the RTEMS RAM Workspace.  The following illustrates the data space required for all configurations of RTEMS:

  * Data Space: 723

Minimum and Maximum Code Space Requirements
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A maximum configuration of RTEMS includes the core and all managers, including the multiprocessing manager. Conversely, a minimum configuration of RTEMS includes only the core and the following managers: initialization, task, interrupt and fatal error.  The following illustrates the code space required by these configurations of RTEMS:

  * Minimum Configuration: 18,980

  * Maximum Configuration: 36,438

RTEMS Code Space Worksheet
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The RTEMS Code Space Worksheet is a tool provided to aid the RTEMS application designer to accurately calculate the memory required by the RTEMS run-time environment.  RTEMS allows the custom configuration of the executive by optionally excluding managers which are not required by a particular application.  This worksheet provides the included and excluded size of each manager in tabular form allowing for the quick calculation of any custom configuration of RTEMS.  The RTEMS Code Space Worksheet is below:

RTEMS Code Space Worksheet

RTEMS RAM Workspace Worksheet
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The RTEMS RAM Workspace Worksheet is a tool provided to aid the RTEMS application designer to accurately calculate the minimum memory block to be reserved for RTEMS use.  This worksheet provides equations for calculating the amount of memory required based upon the number of objects configured, whether for single or multiple processor versions of the executive.  This information is presented in tabular form, along with the fixed system requirements, allowing for quick calculation of any application defined configuration of RTEMS. The RTEMS RAM Workspace Worksheet is provided below:

RTEMS RAM Workspace Worksheet