Keil Cx51 Compiler

Preprocessor Symbols

Define

Sets preprocessor symbols which may be checked with #if, #ifdef and #ifndef. The defined names are copied exactly as they are entered (case-sensitive). Each name may get optionally a value. Define: Check, NoExtRam, X1=1+5 is identical to the following C preprocessor #define statements:
   #define Check
   #define NoExtRam
   #define X1 1+5

Undefine

Undefine clears previous Define assignments that are entered in the options dialog of a higher Target or Group level.

Code Optimization

Level

Set the optimization level the Compiler uses when generating object code.

Emphasis

Specify whether the Compiler should optimize for code size or execution speed.

Global Register Coloring

Enable application wide register optimization. When set the c51 compiler knows the registers used by external functions and µVision performs automatically iterative re-translations of C source files to improve the register allocation.

Linker Code Packing (max. AJMP / ACALL)

Instructs the compiler to include information in the object file for the linker-level program optimizations. When enabled, the LX51 linker/locater performs this optimizations.

Don't use absolute register accesses

Disables absolute register addressing for registers R0 through R7 which allows function calls from different register banks. The code will be slightly longer, since C compiler cannot use ARx symbols, i.e. in PUSH or POP instructions and needs to insert replacement code. However the code will be independent of the selected register bank.

Other Controls

Warnings

Lets you to suppress compiler warnings.

Bits to round for float compare

Determines the number of bits rounded before a floating-point compare is executed. The default value of 3 specifies that the three least significant bits of a float value are rounded before the floating-point compare is executed.

Interrupt vectors at address

Instructs the C Compiler to generate interrupt vectors for interrupt functions and specifies the base address for the interrupt vector table.

Keep Variables in Order

Order all variables in memory according to their order of definition in the C source file.

Enable ANSI integer promotion rules

Expressions are promoted from smaller types to integer expressions before the operation is performed. Integer promotion is normally enabled to provide the greatest compatibility between Cx51 and other ANSI compilers

Include Paths

Allows you to supply one or more (separated by semi-colon) paths to search for header files. For #include "filename.h" the Compiler searches first the current folder and then folder of the source file. When this fails or when #include <filename.h> is used, the paths specified in the include paths box are searched. When this still fails, the paths specified in for the INC folder under Project - Components, Environment, Books ... are used.

Misc Controls

Specify any directive for which there is no individual dialog control.

Compiler Control String

Display the current directives at the Compiler command line.