RTEMS 4.6.4 On-Line Library

Timer Driver Read_timer

BSP and Device Driver Development Guide

10.1.2: Read_timer

The Read_timer routine returns the number of benchmark time units (typically microseconds) that have elapsed since the last call to Timer_initialize.

int Read_timer(void)
{
  stop time = read the hardware timer
  if the subtract overhead feature is enabled
    subtract overhead from stop time
  return the stop time
}

Many implementations of this routine subtract the overhead required to initialize and read the benchmark timer. This makes the times reported more accurate.

Some implementations report 0 if the harware timer value change is sufficiently small. This is intended to indicate that the execution time is below the resolution of the timer.

BSP and Device Driver Development Guide