I am using Altera Stratix FPGA ,Quartus 10.1 version and Nichestack IP for TCP/IP communication. here in a while loop where i am doing some processing ,i want to measure time . for that I am putting alt_timestamp_start()and alt_timestamp( ) functions. besides regular header files I am adding "sys/alt_timestamp.h" and "alt_types .h" header files. but it is showing error as unrefrenced variable to these functions.i want to know which header files i have to add for these functions?