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C51: re-use Library Functions from a Boot Application


Information in this article applies to:

  • Keil C51 Version 8.00
  • Keil PK51 Professional Developer's Kit

QUESTION

I am writing a BOOT code that contains certain library functions. I want to locate this library functions on specific addresses so that I can re-use them in the application (without the need to duplicate them into each application).

However, all intrinsic library functions of the C51 run-time library share the same segment name ?C?LIB_CODE, which makes it practically impossible to locate them individually using linker directives.

Is there a smart solution to my problem?

ANSWER

Yes, take a look at Application Note 180: Multi-Application Programming for 8051 Devices. This application note contains two files:

  • App1Entry.asm: Defines the functions that are in the BOOT section of your code that will be re-used in the APPLICATION section.
  • App1Call.asm: Contains only entry point definitions for the BOOT section. This module is located in the APPLICATION section of your code.

The example in the application note implements a jump table that allows modifications of the BOOT part independent of the APPLICATION part. This technique even allows you to update the BOOT section after the APPLICATION has been released.

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Last Reviewed: Thursday, February 25, 2021


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