This is a problem of warning 16. i have tried the solution given in keil site " This warning occurs when functions which are not called are contained in a program (e.g. for test purposes). The function specified is excluded from the overlay process in this case. Often this warning is accompanied by ERROR 107: ADDRESS SPACE OVERFLOW If you fix the uncalled warning the Error 107 is often cleared as well. There are two ways to solve this problem. 1. Call the uncalled function from somewhere in your program. 2. Remove or #if out the function that is not called. You can do that using #if 0 in front of and #endif after the uncalled function. For example: #if 0 void uncalled_function (void) { } #endif" even after each one of above the problem persists. Would you please throw some light. The errors are pasted as below. *** WARNING 16: UNCALLED SEGMENT, IGNORED FOR OVERLAY PROCESS SEGMENT: ?PR?RI2C_SLAVEADDRESSRECEIVED?RI2C_DCN *** WARNING 16: UNCALLED SEGMENT, IGNORED FOR OVERLAY PROCESS SEGMENT: ?PR?RI2C_SLAVESEND?RI2C_DCN *** WARNING 16: UNCALLED SEGMENT, IGNORED FOR OVERLAY PROCESS SEGMENT: ?PR?RI2C_SLAVERECEIVE?RI2C_DCN *** WARNING 16: UNCALLED SEGMENT, IGNORED FOR OVERLAY PROCESS SEGMENT: ?PR?_MOVXD0?CLIB *** ERROR 107: ADDRESS SPACE OVERFLOW SPACE: DATA SEGMENT: ?DT?TEXTVARS LENGTH: 0001H *** ERROR 118: REFERENCE MADE TO ERRONEOUS EXTERNAL SYMBOL: TXTREQ MODULE: ..\APPLIC\LIB\T90PTR1.LIB (TXREVEAL) ADDRESS: A13CH