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Memory map behavior for BL51

Tom Lin

Hi All:

I use Keil uVision3.I setup BL51 Locate:
code range:0x80-0x3EFF
Xdata range:0x3E00-0x3FFF,0xE000-0xE1FF

I want to compile a .c file like this:

BYTE xdata array1[2];
BYTE xdata UsbBuffer[512];

but I get some Error Message:
*** ERROR L107: ADDRESS SPACE OVERFLOW SPACE: XDATA SEGMENT: ?XD?BULKEXT LENGTH: 0202H

If I remove array[2] and compile,It will be OK.
I don't know why BL51 not Locate array[2] to another memory block(0x3E00-0x3FFF)?

Parents Reply Children
  • 0 in reply to ²erik malund


    then the first thing 'grabbed' from the xdata are the local variables.

    just for show, enlarge the area a bit so the error disappears and look at the map

    If I define Global variable like this: BYTE xdata UsbBuffer[512];
    memory map will be:
    TYPE BASE LENGTH RELOCATION SEGMENT NAME
    XDATA E000H 0200H UNIT ?XD?BULKEXT

    If I define Global variable like this: BYTE xdata UsbBuffer[512]; BYTE xdata array1[2];

    it will Error:*** ERROR L107: ADDRESS SPACE OVERFLOW SPACE: XDATA SEGMENT: ?XD?BULKEXT LENGTH: 0202H

    If I change xdata range:0x3D00-0x3FFF,0xE000-0xE1FF,
    it will be OK.
    memory map will be:
    TYPE BASE LENGTH RELOCATION SEGMENT NAME
    XDATA 3D00H 0202H UNIT ?XD?BULKEXT

  • 0 in reply to ²erik malund

    If I define like this:

    BYTE xdata UsbBuffer[512]; //Global variable
void TD_Poll(void){
BYTE xdata array1[2];
array1[0]=0;
array1[1]=1;
PA2=array1[0]; //LED1
PC1=array1[1]; //LED2
}

    and xdata range is 0x3F00-0x3FFF,0xE000-0xE1FF,It will be OK,memory map like this:
    TYPE BASE LENGTH RELOCATION SEGMENT NAME XDATA 3F00H 0002H UNIT _XDATA_GROUP_ XDATA E000H 0200H UNIT ?XD?BULKEXT

    why?it can place global variables and local variables on different memory block!

    If I move UsbBuffer[512];

     to local variable,it will overflow.

If I change xdata range is 0x3D00-0x3FFF,0xE000-0xE1FF,it will add _XDATA_GROUP size and ?XD?BULKEXT disappear.

  • 0 in reply to ²erik malund

    If I use _at_ keyword will OK.
    xdata range:0x3F00-0x3FFF, 0xE000-0xE1FF
    code like this:

    BYTE xdata UsbBuffer[512];
BYTE xdata array[2] _at_ 0x3F00;

    memory map:
    TYPE BASE LENGTH RELOCATION SEGMENT NAME XDATA 3F00H 0002H ABSOLUTE XDATA E000H 0200H UNIT ?XD?BULKEXT

    but...why BL51 can't locate array[2] to another memory block(0x3E00-0x3FFF) by itself?

  • 0 in reply to Tom Lin

    but...why BL51 can't locate array[2] to another memory block(0x3E00-0x3FFF) by itself?
    it can't because there are some loval variables there already.

    I GUESS the linker does absolutes first, thus when using _at_ you force the locals to the other region. switching to small will probably fix the problem