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

16-Bit C Compiler User’s Guide
For example, to declare two variables that retain their values across a device reset:
int _PERSISTENT var1,var2;
7.6.4 ISR Declaration Macros
The following macros can be used to declare Interrupt Service Routines (ISRs):
#define _ISR __attribute__((interrupt))
#define _ISRFAST __attribute__((interrupt, shadow))
For example, to declare an ISR for the timer0 interrupt:
void _ISR _INT0Interrupt(void);
To declare an ISR for the SPI1 interrupt with fast context save:
void _ISRFAST _SPI1Interrupt(void);
Note: ISRs will be installed into the interrupt vector tables automatically if the
reserved names listed in Section 8.4 “Writing the Interrupt Vector” are
used.
7.7 ACCESSING EEDATA FROM C CODE - dsPIC30F DSCS ONLY
The compiler provides some convenience macro definitions to allow placement of data
into the devices EE data area. This can be done quite simply:
int _EEDATA(2) user_data[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
user_data will be placed in the EE data space reserving 10 words with the given initial
values.
The dsPIC DSC device provides two ways for programmers to access this area of
memory. The first is via the program space visibility window. The second is by using
special machine instructions (TBLRDx).
7.7.1 Accessing EEDATA via the PSV
The compiler normally manages the PSV window to access constants stored in
program memory. If this is not the case, the PSV window can be used to access
EEDATA memory.
To use the PSV window:
• The PSVPAG register must be set to the appropriate address for the program
memory to be accessed. For EE data this will be 0xFF, but it is best to use the
__builtin_psvpage() function.
• The PSV window should also be enabled by setting the PSV bit in the CORCON
register. If this bit is not set, uses of the PSV window will always read 0x0000.
DS51284H-page 96 © 2008 Microchip Technology Inc.