MPLAB C Compiler for PIC24 MCUs and dsPIC DSCs ... - Microchip

7.5 USING SFRS
Device Support Files
There are three steps to follow when using SFR’s in an application.
1. Include the processor header file for the appropriate device. This provides the
source code with the SFR’s that are available for that device. For instance, the
following statement includes the header files for the dsPIC30F6014 part:
#include
2. Access SFR’s like any other C variables. The source code can write to and/or
read from the SFR’s.
For example, the following statement clears all the bits to zero in the special
function register for Timer1.
TMR1 = 0;
This next statement represents the 15th bit in the T1CON register which is the
“timer on” bit. It sets the bit named TON to 1 which starts the timer.
T1CONbits.TON = 1;
3. Link with the register definition file or linker script for the appropriate device. The
linker provides the addresses of the SFR’s. (Remember the bit structure will have
the same address as the SFR at link time.) Example 6.1 would use:
p30f6014.gld
See “MPLAB ® Assembler, Linker and Utilities for PIC24 MCUs and dsPIC ® DSCs
User’s Guide” (DS51317) for more information on using linker scripts.
The following example is a sample real time clock. It uses several SFR’s. Descriptions
for these SFR’s are found in the p30f6014.h file. This file would be linked with the
device specific linker script which is p30f6014.gld.
© 2008 Microchip Technology Inc. DS51284H-page 93