Lpc2000

At 11:37 AM 5/25/05 -0400, Brett Delmage wrote:
>Now, can anyone tell me if there is clean, way to generate faster code than:
>
>#define REG(addr) (*(volatile unsigned long *)(addr))
>#define REG8(addr) (*(volatile char *)(addr))
>
>in gcc? I don't like the multiple instruction to generate the address
>each access, but maybe that is typical/not bad. I'm
>relatively new to ARM and RISC.

I haven't done a comparison of code generation but I use ld in combination 
with gcc for this.

IE in the appropriate ld control file I have something like

/* SYSTEM CONTROL BLOCK */
         /* MAM */

PROVIDE( MAMCR = 0xE01FC000);
PROVIDE( MAMTIM = 0xE01FC004);


PROVIDE( MEMAP = 0xE01FC040);


then in a header file
/* SYSTEM CONTROL BLOCK */
         /* MAM */

extern unsigned char MAMCR;
extern unsigned char MAMTIM;


extern unsigned char MEMAP;

And to reference them in a source file, after including the appropriate 
header of course,

  MAMCR = (unsigned char)ctrl;           /*lint !e930 cast from enum     */
  MAMTIM = (unsigned char)cycle_time;


I find that 'cleaner' than pointer de-references.  YMMV  The biggest 
disadvantage is you end up depending on both the ld file and the header 
file.  I don't know how the code generation compares.

You can see this in the newlib-lpc source.

Robert

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