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uVision4 Debugger's "Memory 1" Window doesn't show the updated value

Khai Lai

I tried to write a simple program that can find the 1's complement of a number and store the result in memory.

This is my program:

;Find the one's complement (inverse) of a number

        TTL     Ch4Ex2 - invert
        AREA    Program, CODE, READONLY
        ENTRY

Main
        LDR     R1, Value       ; Load the number to be complemented
        MVN     R1, R1          ; take 1's complement of R1
        STR     R1, Result      ; Store the result
        SWI     &11

Value   DCD     &FF             ; Value to be complemented
Result  DCD     &ABCD1234       ; Storage for result

        END

When I ran the debugger, I used "Memory 1" window to check the content of Result. But the content of Result didn't change. It kept remained as 0xABCD1234. Can anybody tell me what did I do wrong here?

I am using Keil uVision4 and LPC2368 as my device.

Thank you,
Khai

Parents
  • 0 in reply to Non Keil Related

    No I didn't use any startup code. I guess maybe that's why the contents weren't initialized correctly. However I tried to manually initialize the contents by adding the following code at the beginning of the program that you gave me:

                    LDR             R0,=Value
                MOV             R1,#0xFF
                STR             R1,[R0]

                LDR             R0,=Result
                MOV             R1,#0xABCD1234
                STR             R1,[R0]

    But then I got an error message like this:

    Build target 'Target 1'
assembling One_compl_main.asm...
One_compl_main.asm(14): error: A1510E: Immediate 0xABCD1234 cannot be represented by 0-255 and a rotation
Target not created

    Could you tell me why I got this error message? I thought registers in the ARM are 32-bit long. Why did it say "cannot be represented by 0-255"?

Reply
  • 0 in reply to Non Keil Related

    No I didn't use any startup code. I guess maybe that's why the contents weren't initialized correctly. However I tried to manually initialize the contents by adding the following code at the beginning of the program that you gave me:

                    LDR             R0,=Value
                MOV             R1,#0xFF
                STR             R1,[R0]

                LDR             R0,=Result
                MOV             R1,#0xABCD1234
                STR             R1,[R0]

    But then I got an error message like this:

    Build target 'Target 1'
assembling One_compl_main.asm...
One_compl_main.asm(14): error: A1510E: Immediate 0xABCD1234 cannot be represented by 0-255 and a rotation
Target not created

    Could you tell me why I got this error message? I thought registers in the ARM are 32-bit long. Why did it say "cannot be represented by 0-255"?

Children
  • 0 in reply to Khai Lai

    You need to look at your ARM reference guide for details on that one.

    Esentially, the immediate data is contained within the instruction itself. The instruction and data fit into a 32 bit wide instruction - there are only a small proportion of those bits available for the immediate data.

    The following should work:

        LDR             R0,=Value
    MOV             R1,#0xFF       ; You can leave alone (data fits into instruction)
    STR             R1,[R0]

    LDR             R0,=Result
    MOV             R1,=0xABCD1234 ; Use a pseudo-op
    STR             R1,[R0]