Keil Logo

Version 6.0 Differences

  • EXTERNAL and SEGMENT limitations removed
    The number of external symbols and segments per module are no longer limited to 256. This historical limitation was imposed by the old Intel Object File format.
  • First 256 characters of a variable name are significant
    Now the first 256 characters of a variable name are significant. Previously, only the first 32 characters were significant.
  • Support for NXP 80C51MX and Dallas Contiguous Mode
    Cx51 provides support for the NXP 80C51MX architecture and the Dallas Contiguous Mode that is available on the Dallas 390 and variants.
  • OMF2 directive and far memory type support
    The OMF2 directive enables generation of a new OMF file format that provides detailed symbol type checking across modules and supports up to 16MB code and xdata memory. This format is required when you use the STRING, VARBANKING, and XCROM directives.
  • STRING directive
    The STRING directive locates constant strings in xdata const or far const space. This leaves more code space available for program code.
  • USERCLASS directive
    Assigns user defined class names to compiler generated segments. Class names may be referenced by the LX51 Linker to locate all segments with a specific class name.
  • VARBANKING directive and far memory type support
    Two new memory types, far and const far, and user configurable access routines provide support for up to 16MB extended code and xdata memory. The VARBANKING directive enables far memory type support.
  • XCROM directive
    The XCROM directive locates constants into xdata ROM which frees code ROM space for program code.
  • Support for Analog Devices B2 series of MicroConverters
    The B2 series of ADuC devices contains dual DPTR and an extended stack.


  • Only the the PK51 Professional Developers Kit supports the OMF2 output file format, NXP 80C51MX, Dallas Contiguous Mode, and VARBANKING. These options are not available in the CA51 and DK51 packages.
  Arm logo
Important information

This site uses cookies to store information on your computer. By continuing to use our site, you consent to our cookies.

Change Settings

Privacy Policy Update

Arm’s Privacy Policy has been updated. By continuing to use our site, you consent to Arm’s Privacy Policy. Please review our Privacy Policy to learn more about our collection, use and transfers
of your data.