example_x_space_modulo_buffer.c

Mplab C30编译器

 /* Example illustrating how to create and incrementing modulo buffer
    in X Data Space. The example also shows how to create an
    decrementing modulo buffer in Y Data Space */

 /***********************************************************************
 *  An incrementing modulo buffer for use in assembly language can be   *
 *  easily defined in C. In this example, the macro _XBSS is used to    *
 *  define an array whose memory alignment is the smallest power of     *
 *  two that is greater than or equal to its size. _XBSS is defined in  *
 *  the processor header file, which in this example is p30f6014.h.     *
 *                                                                      *
 *  A decrementing modulo buffer for use in assembly language can be    *
 *  easily defined in C. In this case, the ending address +1 of the     *
 *  array must be aligned. There is not a suitable predefined macro     *
 *  in the processor header files for this purpose, so variable         *
 *  attributes are specified directly. The far attribute is recommended *
 *  because Y memory does not fall within the near space on all devices,*
 *  and the compiler uses a small-data memory model by default.         *
 *                                                                      *
 *  You can view the results of the printf statements by enabling the   *
 *  MPLAB SIM tool then enabling the UART1 I/O with Output set to       *
 *  Window. The printf results are then displayed in the output window. *
 *                                                                      *
 *  A defined heap size is required since we are using a standard I/O   *
 *  function.                                                           *
 *                                                                      *  
 *  For additional information about dsPIC architecture and language    *
 *  tools, refer to the following documents:                            *
 *                                                                      *
 *  MPLAB C30 Compiler User's Guide                        : DS51284    *
 *  dsPIC 30F MPLAB ASM30, MPLAB LINK30 and Utilities                   *
 *                                           User's Guide  : DS51317    *
 *  Getting Started with dsPIC DSC Language Tools          : DS51316    *
 *  dsPIC 30F Language Tools Quick Reference Card          : DS51322    *
 *  dsPIC 30F 16-bit MCU Family Reference Manual           : DS70046    *
 *  dsPIC 30F Programmer's Reference Manual                : DS70030    *
 *                                                                      *
 *  Example file has been compiled with MPLAB C30 v1.30.00              *
 *                                                                      *
 ************************************************************************
 *                                                                      * 
 *    Author:                                                           *
 *    Company:                                                          * 
 *    Filename:       Ex_X_Space_Modulo_Buffer.c                        *
 *    Date:           02/01/2005                                        *
 *    File Version:   1.00                                              *
 *    Other Files Required: p30f6014.gld                                *
 *    Tools Used: MPLAB IDE -> 7.01.00                                  *
 *                Compiler  -> 1.30.00                                  *
 *                Assembler -> 1.30.00                                  *
 *                Linker    -> 1.30.00                                  *
 *                                                                      *
 ***********************************************************************/

 /* Include the appropriate header (.h) file, depending on device used */
 /* Example (for dsPIC30F5013): #include <p30f5013.h>                  */
 /* Alternatively include the generic header file, p30fxxxx.h, as shown 
    below.                                                              */

	/* load SFR definitions and macros */
	#include "p30fxxxx.h"
	#include "stdio.h"

/* define/declare array aligned in X Data Space */
int _XBSS(128) xbuf[50];

/* define/declare array aligned in Y Data Space */
int __attribute__((space(ymemory), far, reverse(128))) ybuf[50];



int main( void )
{
	printf("Should be zero: %x\n", (int) &xbuf % 128);

	printf("Should be zero: %x\n", ((int) &ybuf + sizeof(ybuf)) % 128);
	
	while( 1 );
}


/*  
    // CREATING AN INCREMENTING MODULO BUFFER IN X MEMORY

    The equivalent definition in assembly language appears below. The 
    section alignment could have specified with a separate .align 
    directive. By using * as a section name, the linker is afforded 
    maximum flexibility to allocate memory.

       .global _xbuf
       .section *,xmemory,bss,align(128)
_xbuf: .space 100

    
    // CREATING AN DECREMENTING MODULO BUFFER IN Y MEMORY

	The equivalent definition in assembly language appears below. 
	Reverse section alignment can only be specified as an argument 
	to the .section directive.

        .global _ybuf
        .section *,ymemory,reverse(128)
_ybuf:  .space 100

*/