Lpc2000

On Tuesday 29 March 2005 16:53, rockraj_2003 wrote:
> Hello Friends,
>
> I am using IAR EMBEDDED WORKBENCH.
> The code shown below is produced by the IAR compiler.
> I want to know what is the offset & how they are using the OFFSET in
> PC.
>
> Can any one explain me the below program.
>
>
>  MEMMAP = 2;
>       LDR          R0, [PC,#0x354] [0x68C] =MEMMAP (0xE01FC040)
>       MOV          R1, #2
>       STRB         R1, [R0, #0]
>
>   PINSEL0  = 0x0000000A;
>  0x0000033C 48D4      LDR          R0, [PC,#0x350]; [0x690] =PINSEL0
> (0xE002C000)
>  0x0000033E 210A      MOV          R1, #10
>  0x00000340 6001      STR          R1, [R0, #0]
>
>
> Explain me the LDR & how it points to this address.0xE01FC040
>
>       LDR          R0, [PC,#0x354] [0x68C] =MEMMAP (0xE01FC040)

This is using what is called a literal pool. The actual address is not part 
of the instruction, but is stored.

When you write code like this you do it as follows:
   ldr r0, =0xE01FC040

The assembler then saves the value futrther on in the .text segment and sets 
up an instruction to point to that using an offset relative to the PC.

ie.

    ldr r0,[PC,#offset_to_where_value_is_stored]

value_stored_here:
          .word  0xE01FC040






>
> kindly help me,
>
> with regards,
> Rajendra R
>
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