2.9.1.10 - System Timer Low/High Read (Modes 10 & 11) [U6 Datasheet]

Any idea why I might be getting strangely low timer values on occasion?  For the majority of my sys timer value requests, I get good data.  But sometimes, the LOWER value is an order of magnitude suspiciously low.

Here's my init code, run once before timing/counting begins:

int InitSystemTimer(counter_struct* counter)

{

// Configure Timer0 as system timer low

AddRequest(ljHandle, LJ_ioPUT_TIMER_MODE, X123_TLSW, LJ_tmSYSTIMERLOW, 0, 0);

// Configure Timer1 as system timer high

AddRequest(ljHandle, LJ_ioPUT_TIMER_MODE, X123_TMSW, LJ_tmSYSTIMERHIGH, 0, 0);

// now send all the messages

GoOne(ljHandle);

ePut(ljHandle, LJ_ioPUT_COUNTER_RESET, X123_COUNTER, TRUE, 0);

// flush last value

eGet(ljHandle, LJ_ioGET_COUNTER, X123_COUNTER, &counter->counts, 0);

// init the ticks 

GetCountTime(counter);

counter->ticksInit = counter->ticks;

}

And here's my timer function that I run once a second thereafter:

int GetCountTime(counter_struct* counter)

{

// set up counter read

AddRequest(ljHandle, LJ_ioGET_COUNTER, X123_COUNTER, 0, 0, 0);

// set up read of internal system timer low and high words

AddRequest(ljHandle, LJ_ioGET_TIMER, X123_TLSW, 0, 0, 0);

AddRequest(ljHandle, LJ_ioGET_TIMER, X123_TMSW, 0, 0, 0);

// send all requests

GoOne(ljHandle);

// now get the results

GetResult(ljHandle, LJ_ioGET_COUNTER, X123_COUNTER, &counter->counts);

GetResult(ljHandle, LJ_ioGET_TIMER, X123_TLSW, &lower);

GetResult(ljHandle, LJ_ioGET_TIMER, X123_TMSW, &upper);

// combine timer MSW and LSW

counter->ticks = lower + upper * pow(2, 16);

// calculate the delta time

counter->time = (counter->ticks - counter->ticksInit) / LABJACK_SYS_TIMER_CLOCK;

}

I should have said that I'm using a U6, with latest firmware.  I'm polling the timers at 1Hz with CVI LabWindows.  I output my structure time value and it shows a very close 1HZ rate most of the time, with LABJACK_SYS_TIMER_CLOCK defined as 4e6.

I'm seeing these bad readings maybe once every 4-5 attempts of a unit test.  In a unit test, there's about 500 timer requests.  So it's pretty rare, but often enough that my unit test gets pretty fouled up.  I'm at such a loss as to why the value would be borked.  My counter structure is made up of all doubles.

typedef struct

{

double counts,

ticks,

ticksInit,

time,

rate;

} counter_struct;

I have not been able to reproduce the error, but I think I have found what was causing it. Please send an email so that I can send you a new firmware version to try. The data set requested above may still be useful.

If I do the math on the last three lines I get the following:

19, 4288582525 = 85,892,961,149

19, 4293062524 = 85,897,441,148

20, 2615698 = 85,901,961,618

Which looks correct.