ATTEMPT TO DEFINE AN ALREADY DEFINED SYMBOL

Problem :

C:\KEIL\C51\ASM\C8051F120.INC(17): error A10: ATTEMPT TO DEFINE AN ALREADY DEFINED SYMBOL

Resolution :

The problem here is by default keil defines 8051 registers.

Solution

$NOMOD51 ;ask keil not to define 8051 registers
$INCLUDE (REG320.DEF) ; include your processor definition file.