C51: Is STARTUP.A51 Required?

Information in this article applies to:

• C51 Version 5.50a
• C51 Version 6.00 Beta
• C51 Version 6.00

QUESTION

I'm creating a project that is made up of C and assembly files. Do I need to use the STARTUP.A51 file that you provide, or can I use my own version?

ANSWER

We strongly urge you to use the STARTUP.A51 file that we provide as the basis for your startup routines. The Keil startup code performs the following operations:

• Clears DATA and optionally PDATA and XDATA memory,
• Sets up the reentrant stacks (if necessary)),
• Initializes C Global Variables (see INIT.A51),
• Sets the Stack Pointer (SP),
• Jumps to your MAIN C function.

Your startup code must do all of these. If it doesn't, you may encounter run-time problems that are difficult to debug and diagnose.

Note that if you do not include some form of a startup file, Keil will automatically include a startup file from the Keil library.

SEE ALSO

• C51: Modifying the Startup Routines
• C51: Stack Pointer Initialization in Startup Code
• C51: Avoiding Startup Initialization of Static Variables
• C51: When/Where Are Global and Static Variables Initialized?
• C51: Contents of The ?C_INITSEG Segment

Last Reviewed: Thursday, February 25, 2021