C51: Initializing an Absolutely Located Variable

Information in this article applies to:

• C51 version 5.50 and later

QUESTION

I have declared a global variable using:

unsigned char xdata foo _at_ 0x2000 = 5;

However, upon compilation I get the following error:

Error 274: 'foo': absolute specifier illegal

How can I initialize an absolutely located variable?

ANSWER

You cannot both specify a location for a variable and initialize it at the same time. The best solution is to initialize the variable separately in an initialization routine. For example:

void init_globals(void)
{
  foo = 5;
}

which is then called from the main function.

MORE INFORMATION

• Refer to Absolute Variable Location in the Cx51 User's Guide.

SEE ALSO

• C51: Locating Initialized Variables at Absolute Addresses
• C51: Avoiding Startup Initialization of Static Variables
• BL51: Initializing & Locating a Variable to a Fixed Address

Last Reviewed: Thursday, February 25, 2021