xdata problem -help please

Im trying to get my 87C51 to read and write data to a peripheral (D71055).
I'm using uVision3 and everything works fine with the debugger- I can see the data at the memory locations (0xF801) changing correctly as well as the other program functions.
When I actually program the 87C51 chip and test it everything else works OK, but theres nothing on the D71055)
I'm using
volatile unsigned char xdata D71055_port_a_at_0xF800
volatile unsigned char xdata D71055_port_b_at_0xF801

ps. I've had success (data at 0xF801 reflects whats at 0xF800 correctly) with using a monitor program (paulmon) but I dont want to have that in my chip.

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  • Did you copy those lines direct from your source code and paste into the forum?

    Does your source code really contain these lines?

    volatile unsigned char xdata D71055_port_a_at_0xF800
    volatile unsigned char xdata D71055_port_b_at_0xF801
    

    If it does, they define variables called D71055_port_a_at_0xF800 and D71055_port_b_at_0xF801 at unspecified locations in XDATA...

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  • Did you copy those lines direct from your source code and paste into the forum?

    Does your source code really contain these lines?

    volatile unsigned char xdata D71055_port_a_at_0xF800
    volatile unsigned char xdata D71055_port_b_at_0xF801
    

    If it does, they define variables called D71055_port_a_at_0xF800 and D71055_port_b_at_0xF801 at unspecified locations in XDATA...

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