Analog Devices ee-32 Application Notes

Engineer To Engineer Note EE-32

Notes on using Analog Devices’ DSP, audio, & video components from the Computer Products Division

Phone: (800) ANALOG-D or [phone], FAX: [phone], EMAIL: [e-mail]

Language Extensions: Memory
Storage Types, ASM & Inline
Constructs

Last Modified: 05/11/96

This EE Note has been conceived as guidelines for users
programming our 21xx-DSPs in C. It consists of several
pieces of examples as opposed to a whole project. These
examples have been conceived general-purposed to allow
the users to run them without any piece of hardware, just
using the Simulator. The aim of these guidelines is
namely to illustrate some fundamentals with appropriate
examples, making thus the theory better understandable.

Language extensions

The G21 C compiler supports a set of extensions to the
ANSI standard for the C programming language. These
extensions are specific to the ADSP processors and
comprise:

• Support for separate program and data memory

(keywords pm, dm)

• Support for inline functions

• Support for asm() inlining of assembly language

The following demo code will help illustrate the use of
these extensions and provide further information on them.

LANG_EXT.C

/* lang_ext.c */
/* program demonstrating the use of the G21 extensions */
/* to the C language */

1 #include "pointdef.h" /* contains predefined pointers */

int aux;

static int dm x ; /* placing variables in specific */
static int dm y ; /* memory spaces */

5 static int pm z ;

static int dm i[3]={10,20,30};

DINT pointer; /* DINT is defined in pointdef.h */

/* for a pointer to a dm integer */

static inline int add(void) /* define add() as inline */

a

{

10 z=x+y;

return z;
}

static inline void Set_Fl(short flag) /* define Set_Fl() as inline */

/* this function just sets */
/* Flag 0, 1 or 2 */

{

15 switch (flag)

{
case 0: asm volatile("set fl0;");

break;

case 1: asm volatile("set fl1;");

20 break;

case 2: asm volatile("set fl2;");

break;

}

}

25 static inline void reset_fl1(void) /* to reset Flag 1 and count */

/* the amount of resets */
{
static int pm rst_fl1_count;
rst_fl1_count++;
asm volatile("reset fl1;");

30 }

void main (void)
{ /* several pointer operations */

/* based on the use of the keywords */
/* pm/dm and the file pointdef.h */

pointer=i; /* pointer points to i[0]=10 */
x = *pointer++; /* x=10 ; pointer points to i[1]=20 */

35 aux=(*pointer)++; /* aux=20; i[1]=21; */

y=i[1]; /* y=21 */
add();

Set_Fl(0); /* calling the inline functions */
asm volatile("reset fl0;");

40 Set_Fl(1);

reset_fl1();

asm volatile("toggle fl1;");
reset_fl1();
}

EE-32 Page 2

Notes on using Analog Devices’ DSP, audio, & video components from the Computer Products Division

Phone: (800) ANALOG-D or [phone], FAX: [phone], EMAIL: [e-mail]