HOLD Compiler Directive

HL

Numeric size limits for global variables placed in data, near, and xdata memory. These numbers must be separated by commas and enclosed in parentheses. The HOLD directive has the following format:

HOLD (data_limit [, near_limit [, xdata_limit]])

where:

HOLD (0, 0, 0)

Options — C251 Compiler — Memory Model — Data Allocation Limits.

Use the HOLD directive to specify size limits that the C251 compiler uses when locating global variables that are declared without explicit memory types.

Normally, the C251 compiler locates all variables in the default memory areas defined by the SMALL, LARGE, TINY, XSMALL and XTINY directives. You may use the HOLD directive to store global variables in different memory areas based on the size of the variable.

For example, HOLD(2,4,6) places variables that are 1 or 2 bytes long into data memory, 3 or 4 bytes long into near memory, and 5 or 6 bytes long into xdata memory. Variables that are larger than 6 bytes are stored in far memory. Refer to “251 Memory Areas” 251 Memory Types on page 90 for more information.

Note

• The HOLD directive does not influence the location of automatic variables and static variables declared within a function. When the HOLD directive is active, the default memory type depends on the size of the variable.

When all three HOLD parameters (data_limit, near_limit, xdata_limit) are zero, the C251 compiler uses the default memory type defined by the memory model. Refer to “Memory Models” on page 94 for more information.

Note

• The HOLD directive affects extern definitions. In order for the C251 compiler to determine the location of external variables, you must compile all files in a project with the same HOLD settings. Furthermore, you should explicitly specify array dimensions for extern arrays. Avoid array definitions with empty brackets, for example:

extern int table [];       /* Array size unknown */
                           /* at compile time    */

LARGE, SMALL, TINY, XSMALL, XTINY

C251 SAMPLE.C HOLD (2, 10, 0x2000)

In this example, variables with an object size less than or equal to 2 bytes are stored in data memory, variables with an object size less than or equal to 10 bytes are stored in near memory, and variables with an object size less than or equal to 0x2000 bytes are stored in xdata memory. Objects with larger sizes are stored in the memory model based default memory.

C251 SAMPLE.C HOLD (0, 20)

In this example, variables with an object size 20 bytes and smaller are stored in near data memory. All other variables are stored in far memory.