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Why the following bitwise & doesn't work?

Kevin Wang 

unsigned char tp;
unsigned char volatile pdata HOSTCFG2 _at_ 0x0020;
// HOSTCFG2=0x40 at this point
tp=HOSTCFG2 & 0x40;

//!!! tp is 0x00 instead of 0x40 which is expected

//Corresponding Disassembly:

C:0x08F1    7820     MOV      R0,#HOSTCFG2(0x20)
C:0x08F3    E2       MOVX     A,@R0
C:0x08F4    5440     ANL      A,#HPWRSTATE(0x40)
//Why it refers 0x40 as an address instead of a constant here?
C:0x08F6    F508     MOV      0x08,A
   189:         if ((HOSTCFG2 & 0x40)==0x00)

Thanks.

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  • 0 in reply to erik malund

    Yes. Most tools will just pick the first symbol that matches the value that they see.

    But it doesn't bother me that the symbol is CSTARTUP. It bothers me that the immediate value in the instruction is 0000H when the _at_ keyword assigns the address 1040H.

    The code should read:

    C:0x0800    900000   MOV DPTR,#SomeSymbol(0x1040)

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  • 0 in reply to erik malund

    Yes. Most tools will just pick the first symbol that matches the value that they see.

    But it doesn't bother me that the symbol is CSTARTUP. It bothers me that the immediate value in the instruction is 0000H when the _at_ keyword assigns the address 1040H.

    The code should read:

    C:0x0800    900000   MOV DPTR,#SomeSymbol(0x1040)

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