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NXP 8xC750, 8xC751, and 8xC752

The NXP 8xC750, 8xC751, and 8xC752 derivatives support a maximum of 2 KBytes of internal program memory. The MCU cannot execute LCALL and LJMP instructions. The following must be considered when using these devices:

  • A special library, 80C751.LIB, which does not use these instructions is necessary for these devices.
  • The Cx51 Compiler must be set to avoid using LJMP and LCALL instructions. This is accomplished using the ROM(SMALL)directive.

Note that the following restrictions apply when creating programs for the 8xC750, 8xC751, and 8xC752:

  • Stream functions such as printf and putchar may not be used. These functions are usually not necessary for this chip because it is only equipped with a maximum of 2 KBytes and has no serial interface.
  • Floating-point operations may not be used. Only operations using char, unsigned char, int, unsigned int, long, unsigned long, and bit data types are allowed.
  • The Cx51 Compiler must be invoked with the ROM(SMALL) directive. This control statement instructs the C51 Compiler to use only AJMP and ACALL instructions.
  • The library file 80C751.LIB must be included in the input module list of the linker. For example:
    BL51 myprog.obj, startup751.obj, 80C751.LIB
  • A special startup module, START751.A51, is required. This file contains startup code that is comparable to that found in STARTUP.A51, but contains no LJMP or LCALL instructions. Refer to Customization Files for more information.

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