LX51: Locating Program or Variables to Special Areas

Information in this article applies to:

• C51 Version 7

QUESTION

I am writing an IAP loader and would like to locate it in the first 1024 Bytes of my CODE memory.

How can I ensure this?

I have tried to use wildcards, but this did not work out, since it collides with interrupt vectors.

ANSWER

The best approach is to locate the program code with a USER CLASS. User classes are an extension of the LX51 Linker/Locater (which is available in the PK51 Professional Developer's Kit).

For example, you can write the following pragma within the C source files that contain the IAP loader program code:

#pragma userclass (code = IAP)    // generates CODE_IAP class

This userclass directive places the program code of the module to the memory class CODE_IAP. Now you can separately locate this memory class when you enter it in µVision under Project - Options for Target - LX51 Locate - User Class. To locate the IAP code to the first 1KB of your program section enter here.

CODE_IAP (C:0 - C:0x3FF)

Note, you have to select the Use Extended Linker LX51 under Project - Options for Target - LX51 Locate - User Class.

MORE INFORMATION

• Refer to USERCLASS in the Cx51 User's Guide.
• Refer to CLASSES in the LX51 User's Guide.

SEE ALSO

• C51: Locate a Function at an Absolute Address
• BL51: Locating Groups of Code Segments Together
• LX51: Locating a Segment's Ending Address
• C51: Redirecting Interrupt Vectors

Last Reviewed: Thursday, February 25, 2021