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LARGE Compiler Directive

Abbreviation

LA

Arguments

None.

Default

TINY

µVision

Options — C251 Compiler — Memory Model — Memory Model.

Description

This directive implements the LARGE memory model. In the LARGE memory model, all variables and local data segments of functions and procedures reside (as defined) in the xdata memory of the 251 system. Up to 64 Kbytes of xdata memory may be accessed. This, however, requires the long and therefore inefficient form of data access through the data pointer (DPTR or DR56). The default data pointer size is 4 bytes which allows full access to the entire 251 address space.

Regardless of memory model type, you may declare variables in any of the 251 memory areas. However, placing frequently used variables (such as loop counters and array indices) in data or near memory significantly improves system performance.

Note

  • The stack required for function calls is always placed in near memory, refered as memory class EDATA.
  • Instead of using the LARGE memory model, you should try the XTINY or XSMALL memory model.
See Also

HPTR

Example
C251 SAMPLE.C LARGE

#pragma large
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