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

MPLAB C Compiler for PIC18 MCUs vs. 16-Bit Devices
D.7 STORAGE QUALIFIERS
The PIC18 MCU Compiler uses the non-ANSI far, near, rom and ram type qualifiers.
The 16-Bit Device Compiler uses the non-ANSI far, near and space attributes.
EXAMPLE D-1: DEFINING A NEAR VARIABLE
EXAMPLE D-2: DEFINING A FAR VARIABLE
EXAMPLE D-3: CREATING A VARIABLE IN PROGRAM MEMORY
D.8 PREDEFINED MACRO NAMES
The PIC18 MCU Compiler defines __18CXX, __18F242, ... (all other processors with
__ prefix) and __SMALL__ or __LARGE__, depending on the selected memory model.
The 16-Bit Device Compiler defines __dsPIC30.
D.9 INTEGER PROMOTIONS
D.10 STRING CONSTANTS
D.11 ACCESS MEMORY
D.12 INLINE ASSEMBLY
PIC18 near int gVariable;
16-Bit __attribute__((near)) int gVariable;
PIC18 far int gVariable;
16-Bit __attribute__((far)) int gVariable;
PIC18 rom int gArray[6] = {0,1,2,3,4,5};
16-Bit __attribute__((space(psv)))
const int gArray[6] = {0,1,2,3,4,5};
The PIC18 MCU Compiler performs integer promotions at the size of the largest operand
even if both operands are smaller than an int. This compiler provides the -Oi+
option to conform to the standard.
The 16-Bit Device Compiler performs integer promotions at int precision or greater as
mandated by ISO.
The PIC18 MCU Compiler keeps string constants in program memory in its .stringtable
section. This compiler supports several variants of the string functions. For
instance, the strcpy function has four variants allowing the copying of a string to and
from both data and program memory.
The 16-Bit Device Compiler accesses string constants from data memory or from program
memory through the PSV window, allowing constants to be accessed like any
other data.
16-bit devices do not have access memory.
The PIC18 MCU Compiler uses non-ANSI _asm and _endasm to identify a block of
inline assembly.
The 16-Bit Device Compiler uses non-ANSI asm, which looks more like a function call.
The compiler use of the asm statement is detailed in Section 9.4 “Using Inline
Assembly Language”.
© 2008 Microchip Technology Inc. DS51284H-page 205