Variable Allocation using @ "SegmentName"

The following listing shows a method of directly allocating variables in a named segment, rather than using a #pragma.

Listing: Allocation of Variables in Named Segments

#pragma DATA_SEG __SHORT_SEG tiny
#pragma DATA_SEG not_tiny

#pragma DATA_SEG __SHORT_SEG tiny_b

#pragma DATA_SEG DEFAULT

int i@"tiny";

int j@"not_tiny";

int k@"tiny_b";

With some pragmas in a common header file and with another macro definition, you can allocate variables depending on the macro.

Declaration = <TypeSpec> 
<Declarator>[@"<Section>"][=<Initializer>];

Variables declared and defined with the @"section" syntax behave exactly like variables declared after their respective pragmas.

<TypeSpec> is the type specifier, for example, int or char
<Declarator> is the identifier of your global object, for example, i, glob
<Section> is the section name. Define the section name in the link parameter file as well. For example, "MyDataSection".
<Initializer> is the value to which the global variable is initialized.

Specify the section name using a section pragma before the declaration occurs as shown in the following listings.

Listing: Examples of Section Pragmas

#pragma DATA_SEC __SHORT_SEG  MY_SHORT_DATA_SEC
#pragma DATA_SEC              MY_DATA_SEC

#pragma CONST_SEC             MY_CONST_SEC

#pragma DATA_SEC   DEFAULT // not necessary, but is good practice

#pragma CONST_SEC  DEFAULT // not necessary, but is good practice

int short_var @"MY_SHORT_DATA_SEC"; // OK, accesses are short

int ext_var @"MY_DATA_SEC" = 10; // OK, goes into

                                 // MY_DATA_SECT

int def_var;  / OK, goes into DEFAULT_RAM

const int cst_var @"MY_CONST_SEC" = 10; // OK, goes into MY_CONST_SECT

Listing: Corresponding Link Parameter File Settings (PRM file)

SECTIONS
    MY_ZRAM  = READ_WRITE 0x00F0 TO 0x00FF;

    MY_RAM   = READ_WRITE 0x0100 TO 0x01FF;

    MY_ROM   = READ_ONLY  0x2000 TO 0xFEFF;

    MY_STACK = READ_WRITE 0x0200 TO 0x03FF;

END

PLACEMENT

    MY_CONST_SEC,DEFAULT_ROM INTO  MY_ROM;

    MY_SHORT_DATA_SEC        INTO  MY_ZRAM;

    MY_DATA_SEC, DEFAULT_RAM INTO  MY_RAM;

    SSTACK                   INTO  MY_STACK;

END