Cosmic Software

Cosmic Software Frequently Asked Questions

How do I access global variables declared in C from an Assembly module?

The compiler declares any global variable in C with an underscore (_) prefix. Meaning, if you have a variable declared as:

unsigned char counter;

and wish to access its value in assembly; your assembly code would look something like

xref _counter 
ldab _counter

If the variable is located in the zero page (if supported)

@tiny unsigned char test;
OR
@dir unsigned char test

Then in assembly

xref.b _test 
ldab _test