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Hi All
Anyone Know how the calculation is done in the case of a quad timer. I am using DSP56f801, the IP bus is configured at 40 Mhz. const qt_sState quadParam0= { /* Mode = */ qtCount, /* InputSource = */ qtPrescalerDiv128, /* InputPolarity = */ qtNormal, /* SecondaryInputSource = */ 0, /* CountFrequency = */ qtOnce, /* CountLength = */ qtUntilCompare, /* CountDirection = */ qtDown, /* OutputMode = */ qtAssertWhileActive, /* OutputPolarity = */ qtNormal, /* OutputDisabled = */ 1, /* Master = */ 0, /* OutputOnMaster = */ 0, /* CoChannelInitialize = */ 0, /* AssertWhenForced = */ 0, /* CaptureMode = */ qtDisabled, /* CompareValue1 = */ 0x8000, /* CompareValue2 = */ 0, /* InitialLoadValue = */ 0xFFFF, /* CallbackOnCompare = */ { CallBackOnCompare0, 0 }, /* CallbackOnOverflow = */ { 0, 0 }, /* CallbackOnInputEdge = */ { 0, 0 }} I like to know what will be the time interval with which the callback functions will be called if i use the above configuration. Please give the formula for calculation. Thanks Praveen |
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Question on Quad Timer
Started by ●July 6, 2004
Reply by ●July 6, 20042004-07-06
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RE: [motoroladsp] Question on Quad Timer
for the 56F8xx family, it might be: (65535 - 0) * 128 * 25 = nanoseconds, or 209.712 milliseconds from the time that the counter is enabled. Add to that, context save time, and interrupt latency. 25ns = period for 40MhzCounting.
Jerry. > -----Original Message-----
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Reply by ●July 6, 20042004-07-06
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You take the IPbus and divide by the prescaler to get the
timer period.
Then, you look at the mode to find out how many ticks between
interrupts. Generally it this is equal to the compare value minus the
load value. This can be a little tricky for PWM modes and such. There are 2
compare values for some modes.
Hope this helps.
Howard
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Reply by ●July 7, 20042004-07-07
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Thanks to both of you
Then according to the formula the time should be 0.1 sec .But i used in the following code to switch on /off a LED. just a skeleton code void main() { // LED drivers declared // timer drivers declared count =0 interrupt =TRUE while(1) { if(interrupt = TRUE) { switch(count %2) { case 0 :off case 1: true } } } } // outside main call back function declared { count = count+1; } But the time difference between the LED on /off is around 5 sec.Why so much difference from 0.1 sec to 5 sec. Please reply . Thanks Praveen --- In , "Ebersman, Howard" <HEbersman@m...> wrote: > You take the IPbus and divide by the prescaler to get the timer period. > > Then, you look at the mode to find out how many ticks between interrupts. > Generally it this is equal to the compare value minus the load value. This > can be a little tricky for PWM modes and such. There are 2 compare values > for some modes. > > Hope this helps. > Howard > > -----Original Message----- > From: praveen [mailto:powerarm2001@y...] > Sent: Tuesday, July 06, 2004 4:46 PM > To: > Subject: [motoroladsp] Question on Quad Timer > Hi All > Anyone Know how the calculation is done in the case of a quad timer. > > I am using DSP56f801, the IP bus is configured at 40 Mhz. > > const qt_sState quadParam0= > { > /* Mode = */ qtCount, > /* InputSource = */ qtPrescalerDiv128, > /* InputPolarity = */ qtNormal, > /* SecondaryInputSource = */ 0, > > /* CountFrequency = */ qtOnce, > /* CountLength = */ qtUntilCompare, > /* CountDirection = */ qtDown, > > /* OutputMode = */ qtAssertWhileActive, > /* OutputPolarity = */ qtNormal, > /* OutputDisabled = */ 1, > > /* Master = */ 0, > /* OutputOnMaster = */ 0, > /* CoChannelInitialize = */ 0, > /* AssertWhenForced = */ 0, > > /* CaptureMode = */ qtDisabled, > > /* CompareValue1 = */ 0x8000, > /* CompareValue2 = */ 0, > /* InitialLoadValue = */ 0xFFFF, > > /* CallbackOnCompare = */ { CallBackOnCompare0, 0 }, > /* CallbackOnOverflow = */ { 0, 0 }, > /* CallbackOnInputEdge = */ { 0, 0 }} > > I like to know what will be the time interval with which the > callback functions will be called if i use the above configuration. > > Please give the formula for calculation. > > Thanks > Praveen > > > _____________________________________ > Note: If you do a simple "reply" with your email client, only the author of > this message will receive your answer. You need to do a "reply all" if you > want your answer to be distributed to the entire group. > > _____________________________________ > About this discussion group: > > To Join: > > To Post: > > To Leave: > > Archives: http://www.yahoogroups.com/group/motoroladsp > <http://www.yahoogroups.com/group/motoroladsp> > > More Groups: http://www.dsprelated.com/groups.php3 > <http://www.dsprelated.com/groups.php3 > > <http://us.ard.yahoo.com/SIG97bujej/M)5196.4901138.6071305.300117 6/D=gr > oups/S05771855:HM/EXP89233380/A!28215/R=0/SIGse96mf6/*http: //comp > anion.yahoo.com> click here > > <http://us.adserver.yahoo.com/l? M)5196.4901138.6071305.3001176/D=groups/S= > :HM/A!28215/randT0290140 > _____ > > > . |
