5.4.15. SYS_CLOCK (0x10)

Returns the number of centiseconds since the execution started.

Values returned by this SWI can be of limited use for some benchmarking purposes because of communication overhead or other agent-specific factors. For example, with Multi-ICE the request is passed back to the host for execution. This can lead to unpredictable delays in transmission and process scheduling.

Use this function to calculate time intervals (the length of time some action took) by calculating differences between intervals with and without the code sequence to be timed

Some systems allow more accurate timing (see SYS_ELAPSED (0x30) and SYS_TICKFREQ (0x31)).

Entry

Register r1 must contain zero. There are no other parameters.

Return

On exit, r0 contains:

  • the number of centiseconds since some arbitrary start point, if the call is successful

  • –1 if the call is unsuccessful (for example, because of a communications error).

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