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

EXAMPLE 7-2: EEDATA ACCESS VIA PSV
#include
int main(void) {
PSVPAG = __builtin_psvpage(&user_data);
CORCONbits.PSV = 1;
/* ... */
if (user_data[2]) ;/* do something */
Device Support Files
}
These steps need only be done once. Unless PSVPAG is changed, variables in EE
data space may be read by referring to them as normal C variables, as shown in the
example.
Note: This access model is not compatible with the compiler-managed PSV
(-mconst-in-code) model. You should be careful to prevent conflict.
7.7.2 Accessing EEDATA using TBLRDx instructions
The TBLRDx instructions are not directly supported by the compiler, but they can be
used via inline assembly. Like PSV accesses, a 23-bit address is formed from an SFR
value and the address encoded as part of the instruction. To access the same memory
as given in the previous example, the following code may be used:
To use the TBLRDx instructions:
• The TBLPAG register must be set to the appropriate address for the program
memory to be accessed. For EE data, this will be 0x7F, but it is best to use the
__builtin_tblpage() function.
• The TBLRDx instruction can be accessed from an __asm__ statement or through
one of the __builtin_tblrd functions; refer to the “dsPIC30F/33F
Programmer’s Reference Manual” (DS70157) for information on this instruction.
EXAMPLE 7-3: EEDATA ACCESS VIA TABLE READ
#include
#define eedata_read(src, offset, dest) { \
register int eedata_addr; \
register int eedata_val; \
\
eedata_addr = __builtin_tbloffset(&src)+offset; \
__asm__("tblrdl [%1], %0" : "=r"(eedata_val) : "r"(eedata_addr)); \
dest = eedata_val; \
}
int main(void) {
int value;
TBLPAG = __builtin_tblpage(&user_data);
eedata_read(user_data,2*sizeof(user_data[0]), value);
if (value) ; /* do something */
}
© 2008 Microchip Technology Inc. DS51284H-page 97