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C166: PLACING VARIABLES IN NON-VOLATILE RAM

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Information in this article applies to:

• C166 Version 4
• C166 Version 5

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QUESTION

I use off-chip non-volatile RAM on the C164 microcontroller to save calibration parameters. I need to keep those values safe in memory even in case of software modification.

How can I store a few variables at a fixed memory location? The location must remain at the same place even when I change my software, so that several software revisions use the same configuration data.

ANSWER

The C166 Compiler offers several directives that are required for this:

• The NOINIT compiler directive prevents the clearing of the variables in the startup code.
• The ORDER compiler directive ensures that the variables are stored in the order of their definition.
• You may use the linker location directives to define fixed memory addresses for the variables that are defined in a C source module. In µVision, you may enter section names under Options - L166 Locate - User Sections.

An example that is almost identical to your requirement is in the Getting Started User's Guide, under Creating Applications, Tips and Tricks, Locate Sections to Absolute Memory Locations.

MORE INFORMATION

• Refer to NOINIT in the C166 User's Guide.
• Refer to ORDER in the C166 User's Guide.
• Refer to Linker Location Controls in the C166 User's Guide.
• Getting Started User's Guide

SEE ALSO

• C166: RELOCATE SYSTEM STACK FROM IDATA TO SDATA
• C166: PUTTING INITIALIZED VARIABLES IN XDATA

Last Reviewed: Friday, July 15, 2005

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