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C51: Relocating Program Code in C

Information in this article applies to:

  • C51 All Versions


I have a C51 development software for windows. I want to relocate the program code to an address other than 0000h. How do I do that in C source code? I tried to set the linker code segment address to 8000h, but it did not work.


There are several steps involved in this.

  1. If you haven't already, copy \C51\LIB\STARTUP.A51 into your working directory, and add it to your project as the last file.
  2. In STARTUP.A51 change the CSEG AT 0000H line to be: CSEG AT 8000H
  3. Open the µVision "Options for Target..." window. Select the "Target" tab. Set your Eprom, Start to 0x8000.
  4. On the C51 tab, set "Interrupt vectors at address" to 0x8000.

The next time you build your project, all of your source code will be located at 8000h and above.


Last Reviewed: Thursday, February 25, 2021

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