getting system time in Vxworks

Question

is there anyways to get the system time in VxWorks besides tickGet() and tickAnnounce? I want to measure the time between the task switches of a specified task but I think the precision of tickGet() is not good enough because the the two tickGet() values at the beggining and the end of taskSwitchHookAdd function is always the same!

Answer 1

If you are looking to try and time task switches, I would assume you need a timer at least at the microsecond (us) level.

Usually, timers/clocks this fine grained are only provided by the platform you are running on. If you are working on an embedded system, you can try and read thru the manuals for your board support package (if there is one) to see if there are any functions provided to access various timers on a board.

A more low level solution would be to figure out the processor that is running on your system and then write some simple assembly code to poll the processor's internal timebase register (TBR). This might require a bit of research on the processor you are running on, but could be easily done.

If you are running on a PPC based processor, you can use the code below to read the TBR:

loop: mftbu rx #load most significant half from TBU
mftbl ry #load least significant half from TBL
mftbu rz #load from TBU again
cmpw rz,rx #see if 'old' = 'new'
bne loop #repeat if two values read from TBU are unequal

On an x86 based processor, you might consider using the RDTSC assembly instruction to read the Time Stamp Counter (TSC). On vxWorks, pentiumALib has some library functions (pentiumTscGet64() and pentiumTscGet32()) that will make reading the TSC easier using C.

source: http://www-inteng.fnal.gov/Integrated_Eng/GoodwinDocs/pdf/Sys%20docs/PowerPC/PowerPC%20Elapsed%20Time.pdf

Good luck!

Answer 2

It depends on what platform you are on, but if it is x86 then you can use:

pentiumTscGet64();