I use the Silicon-Lab 8051F321 with Keil LX51 linker: Few compiler library routines are called from the USBXpress library subroutines. These are function like IILDX, CLDPTR, CLDOPTR. I was trying to locate them by using the USER SEGMENT like ?C?IILDX(C:0x1980) ... but the linker does not recognize the segment (maybe because it is not really a USER segment). Any idea how to locate such functions within the code?