C51: Unresolved External Symbol ?C?XPAGE1SFR

Information in this article applies to:

• Cx51 Version 7, or higher

QUESTION

I am using the Dallas 400 in Contiguous Mode.

Why do I get the following linker error messages?

*** ERROR L127: UNRESOLVED EXTERNAL SYMBOL
    SYMBOL:  ?C?XPAGE1SFR
    MODULE:  interr.obj (INTERR)

*** ERROR L127: UNRESOLVED EXTERNAL SYMBOL
    SYMBOL:  ?C?XPAGE1RST
    MODULE:  interr.obj (INTERR)

I have already tried this project with the Dallas 390, but get the same messages. What is wrong?

ANSWER

Most likely, in µVision, the address extension SFR is being saved in interrupts (see Project - Options for Target - Target - Save Address Extension SFR in Interrupts). However, the Dallas Contiguous Mode only requires that you enable far memory support (see Project - Options for Target - Target - 'far' memory type support).

Disable Project - Options for Target - Target - Save Address Extension SFR in Interrupts since the C51 Compiler always saves the DPX register in interrupt functions for Dallas 390 and 400 compatible devices.

MORE INFORMATION

• Dallas Semiconductor App Note 606: Configuring Keil PK51 for 24-bit Contiguous Mode is available on: https://pdfserv.maximintegrated.com/en/an/AN606.pdf

SEE ALSO

• C51: Absolute Access for Far Variables

Last Reviewed: Thursday, February 25, 2021