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Hi, I am currently trying to get my DSP56303EVM board to run at a frequency close to 100Mhz. According to the documentation, Fextal.288Mhz. I have therefore configured the PCTL register with the following value: $50007 This enables PLL operation and sets the XTLD bit. The MF bits take the value of 7. The output clock should therefore be 12.288*(7+1) = 98... Mhz I originally thought this was working well since the frequency counter gave me the correct value. When i tried analyzing CLKOUT using a logic analyzer however, i noticed that the clock was experiencing some little technical difficulties, the duty cycle and clock period varying dramatically from one pulse to the other. Has anyone ever had this problem ? I obviously looked in the motorola documentation and noticed somewhere that it says skew elimination is only guaranteed for MF <= 4. Would this explain my problem or am i just doing something wrong ? Thanks in advance. Guillaume |
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DSP56303EVM and PLL configuration
Started by ●May 23, 2003
Reply by ●May 24, 20032003-05-24
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Currently I am using movep #$050006,X:M_PCTL ; DSP core at 12.288x7 = 86.016MHz in one of my apps running the DSP56364. Maybe the missing leading zero in your value makes the difference.... Please take a look what is stored in your pctl register. I guess $500070 which makes no sense... regards Christian > Hi, > > I am currently trying to get my DSP56303EVM board to run at a > frequency close to 100Mhz. According to the documentation, > Fextal.288Mhz. I have therefore configured the PCTL register with > the following value: $50007 > > This enables PLL operation and sets the XTLD bit. The MF bits take > the value of 7. The output clock should therefore be > > 12.288*(7+1) = 98... Mhz > > I originally thought this was working well since the frequency > counter gave me the correct value. When i tried analyzing CLKOUT > using a logic analyzer however, i noticed that the clock was > experiencing some little technical difficulties, the duty cycle and > clock period varying dramatically from one pulse to the other. > > Has anyone ever had this problem ? > > I obviously looked in the motorola documentation and noticed > somewhere that it says skew elimination is only guaranteed for MF <= > 4. Would this explain my problem or am i just doing something wrong ? > > Thanks in advance. > Guillaume > > _____________________________________ > 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 > > More Groups: http://www.dsprelated.com/groups.php3 > ">http://docs.yahoo.com/info/terms/ -- +++ GMX - Mail, Messaging & more http://www.gmx.net +++ Bitte lheln! Fotogalerie online mit GMX ohne eigene Homepage! |
