Architecture and Instruction Set of the C6x Processor - Digital Signal Processing and Applications with the C6713 and C6416 DSK - page 95

#pragma DATA_SECTION (buffer, “.extRAM”)

is used to place buffe r in the section extRAM . In the linker command file, the
following is specified within SECTIONS:

.extRAM : > SDRAM

and within MEMORY, the following is specified:

SDRAM: org = 0x80000000, len = 0x01000000

where 0x80000000 is the address in external memory (CE0 space). Another useful
pragma directive,

#pragma MUST_ITERATE (20,20)

tells the compiler that the loop following will execute 20 times (a minimum and
maximum of 20 times).

3.17.4 Memory Models

The compiler generates a small memory model code by default. Every data object
is handled as if declared near unless it is specifically declared far . If the
DATA_SECTION pragma is used, the object is specified as a far variable.
How run-time support functions are called can be controlled by the option -mr0
with the run-time support data and calls near , or by the option -mr1 with the run-
time support data and calls far . Using the far method to call functions does not
imply that those functions must reside in off-chip memory.
Large-memory models can be generated with the linker options -mlx ( x = 0 to

4). If no level is specified, data and functions default to near . These models can be
used for calling a function that is more than 1 M word away.

3.18 FIXED- AND FLOATING-POINT FORMAT

Some fixed-point considerations are reviewed in Appendix C.

3.18.1 Data Types

Some data types are:

1. short : of size 16 bits represented as 2's complement with a range from - 2 15

to (2 15 - 1)