© 1997 Microchip Technology Inc.

DS00669A-page 3

AN669

Assembly Language Variables, Include Files,

etc.

For the floating point math routines of AN575, there is

one include file which contains important constant and

register declarations: math16.inc. This file of declara-

tions is rather extensive, however, it is straightforward

to convert it to C. Example 4 shows a segment of the

math16.inc

requiring some attention for the conver-

sion.

EXAMPLE 4:

MATH16.INC EXCERPT

FROM AN575. ASSEMBLY

LANGUAGE FILE

B0

equ

0

B1

equ

1

B2

equ

2

B3

equ

3

B4

equ

4

B5

equ

5

B6

equ

6

B7

equ

7

MSB

equ

7

LSB

equ

0

.

. etc.

.

AARGB7

equ

0x20

AARGB6

equ

0x21

AARGB5

equ

0x22

AARGB4

equ

0x23

AARGB3

equ

0x24

AARGB2

equ

0x25

AARGB1

equ

0x26

AARGB0

equ

0x27

AARG

equ

0x27

; most significant

; byte of argument A

These Constant and Variable Declarations

Need to be Converted to C Language

Declarations

Example 5 shows the equivalent C constant and vari-

able declarations. The equates in assembly language

create constants. The equivalent C language is a

#define

. Moreover, variables are declared in assem-

bly language by equating a variable name to a register

RAM location (i.e. AARGB7 equ 0x20). In C the vari-

ables are declared by assigning a type to the variable.

In the listing in Example 5, AARGB7 is declared as an

unsigned integer data type.

EXAMPLE 5:

THE CONVERTED MATH16C.C FILE. C LANGUAGE FILE

#define

B0

0

#define

B1

1

#define

B2

2

#define

B3

3

#define

B4

4

#define

B5

5

#define

B6

6

#define

B7

7

#define

MSB

7

#define

LSB

0

.

. etc.

.

unsigned int AARGB0 @ ACCB0;

// most significant byte of argument A

unsigned int AARGB1 @ ACCB1;

unsigned int AARGB2 @ ACCB2;

unsigned int AARGB3 @ ACCB3;

unsigned int AARGB4 @ ACCB4;

unsigned int AARGB5 @ ACCB5;

unsigned int AARGB6 @ ACCB6;

unsigned int AARGB7 @ ACCB7;

// least significant byte of argument A

unsigned int AARG

@ ACC;

// most significant byte of argument A