C51: DECLARING 2 VARIABLES AT THE SAME ADDRESS

Information in this article applies to:

• C51 All Versions

QUESTION

I need to declare 2 variables at the same address. What's the best way to do this?

ANSWER

1. In your C code, create external definitions for the variables. For example:

   extern unsigned char xdata var1;
   extern unsigned char xdata var2;
   

2. Create an assembler module that appears as follows:

   xseg at 0x8000
   
   public var1
   public var2
   
   var1:
   var2: DS 1
   
   end
   

   This creates var1 and var2 as 1-byte variables (char or unsigned char) in XDATA at address 0x8000. If you don't want or need to fix the address of the variables, you may create a relocatable segment. For example:

   xdata_junk segment xdata
   rseg xdata_junk
   
   public var1
   public var2
   
   var1:
   var2: DS 1
   
   end
   

Last Reviewed: Saturday, July 09, 2005