ElapsedTime -- returns the time elapsed since it was last called. (V40)

fractionalSeconds = ElapsedTime(context); D0 A0 ULONG ElapsedTime(struct EClockVal *);

This function utilizes the timer.device/ReadEClock() function to get an accurate elapsed time value. Since the context needs to be established the first call to this routine will return a nonsense value. The return value for this function only allows for sixteen bits worth for the integer number of seconds and sixteen bits for the factional number of seconds. With sixteen bits worth of integer seconds this function can be used to timer an interval up to about 16 hours. If the actual time interval is larger this function will return this maximum value. The sixteen bits for fractional seconds gives a resolution of approximately 20 microseconds. However, it is not recomended to expect this function to be accurate for a time interval of less than 200 microseconds.

context - pointer to an EClockVal structure. The first time you call this function, you should initialize the structure to 0s. You should then reuse the same structure for subsequent calls to this function, as this is how the elapsed time is calculated.

fractionalSeconds - The elapsed time as a fixed point 32-bit number with the point fixed in the middle. That is, the upper order sixteen bits represent the number of seconds elapsed. The low order sixteen bit represent the fractional number of seconds elapsed. This value is limited to about sixteen hours. Although this value is precise to nearly 20 microseconds it is only accurate to within 200 microseconds.

The first call to this function will return a non-sense value. Only rely on its result starting with the second call.

Alpha Flight 1970