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DW8051 MPAGE reg

Henrik Holm

Hi,
The Synopsis DW8051 core uses a MPAGE sfr reg at 0x92 hex instead of the standard P2 register when accessing data with MOVX etc.
Do Keil support this register? If so what do I do to enable it?

Regards

Henrik

  • 0

    From the documentation that I have, it appears that the MPAGE register is only used if you do not include a P2 module in your Synopsis design.

    The MPAGE register provides the upper 8 bits for:

    movx a, @r0/@r1
movx @r0/@r1, a

    In the C51 compiler, these instructions are used only in the COMPACT memory model (for PDATA variables).

    In the startup code, there is a section where you may set the value of P2 for all PDATA operations. Change this code to set the value in the MPAGE register.

    Jon

  • 0 in reply to Jon Ward

    "In the C51 compiler, these instructions are used only in the COMPACT memory model (for PDATA variables)."

    Incorrect: the compiler must always use these instructions for any reference to PDATA - that's what PDATA means!

    The effect of the COMPACT memory model is simply to make PDATA the default - you can still explicitly define a variable to be in PDATA in any memory model you want (in fact, some contributors will urge that you should always do so!)

  • 0 in reply to Andrew Neil

    Good point. Thanks for clarifying that.

    What I meant was that MPAGE is only used when you use PDATA variables. PDATA is the default memory space in COMPACT model.

    :-)

    Jon