USERCLASS Compiler Directive

(Memory Space = user_classname)

Memory Space refers to the default memory space used for variables
or program code and is explained below:

user_classname is the name for a memory class.
You may supply any valid identifier for a class name.

The USERCLASS directive assigns a user defined class name to a compiler generated segment. By default, the C51 Compiler uses the basic class name for segment definitions.

The user class name may located at a specific address range by the extended LX51 Linker. This allows you to locate all segments with a class name such as XDATA_FLASH to a specific memory area.

The USERCLASS directive renames the basic class name for an entire module. Overlayable segments (typically local variables in C functions) are not renamed. To rename a local variable, you must change its allocation type to static by including the static keyword in the variable definition. For example:

/* Rename XDATA class to XDATA_MyClass */
#pragma userclass (xdata = MyClass)

xdata int glob_var;          /* Stored in XDATA_MyClass */
static xdata int static_var; /* Stored in XDATA_MyClass */

void func (void)
{
static xdata long func_var;  /* Stored in XDATA_MyClass */
xdata long func_var2;        /* Stored in XDATA */

func_var = 1;
func_var2 = 2;
}

void main (void)
{
static xdata long main_var;  /* Stored in XDATA_MyClass */
xdata long main_var2;        /* Stored in XDATA */

main_var = 1;
main_var2 = 2;

func ();

while (1);
}

Memory classes are only available when you use the OMF2 format and the extended LX51 Linker/Locater.

C51 UCL.C

#pragma userclass (xdata = flash)
#pragma userclass (hconst = patch)

int xdata x1 [10];                // XDATA_FLASH
const char far tst[] = "Hello";   // HCONST_PATCH