AW: [DSP-10] Problems with DSP10 PLL lock

Mon, 05 Aug 2002 13:16:18 +0000

Hi, thanks answering.
Please see my comments below :
>
>Hi Marius
>
>You did not tell us if the unit was fine and running with the original 
>EPROM or not.

The unit did not plot any waterfall diagram or show any information on the 
spectrum analyzer with the original Ezkit eprom that were supplied with the 
kit. That leads me to think there was no communication when i loaded 
UHF3.EXE with the original loader.

When I tried to load the UHF3.EXE with UHF3M21.HEX running on the Ezfast the 
unit DID plot the waterfall diagram and showed information on the spectrum 
analyzer. When I tried to run the code contained in the UHF3M21 without 
transffering UHF3.exe  it appeared that there were no communication. All 
this is based on if the UHFA.EXE application plotted data on the waterfall 
diagram and the spectrum analyzer diagram.

>- Be sure to run the software with a true DOS environment, not DOS in a 
>window in Windows. (Might be the fault)

Hmmm, that might be the problem. I must admit that I did not
boot the PC in MS-DOS modus. I ran a maximized MS-DOS window.
Will try in MS-DOS modus.

>- If the EZ Kit lite board is not initializing the PLL IC's U7 and U104 
>properly, the PLL's are never achieving lock. I attached below a older 
>message about this subject. But the problem was more sporadic than yours. 
>However I could reproduce regularly the effect by using DOS in a Windows 
>window.

Since you are mentioning it, I tried to look at the PLL control lines and I 
could not see any clock or data or latch activity. I thought this 
communication might have been to high speed to easily observe. I did not 
observe any signals on theese PLL control lines even  when resetting the ez 
Kit lite and when running the UHFA.exe on the PC. (Not shure how often and 
at what time the PLL data is outputted to the PLLs)
Can you comment on how easily traffic the PLL control lines are observed 
with a scope ?

>- Pulses on the lock output on both PLL's are normal. There are filters to 
>clean the signal from short duration pulses, so the DC level is restored. 
>But when the pulse pause relationship is wrong, the outputs are signaling 
>PLL unlock.

OK

>- Pin 3 of U8 has a DC voltage of 2.05 Volt in my unit. It seems that your 
>U8 is drawing quite a low current (15mA), which is at the lower end of the 
>specifications. (Looks like the search has to be started there)

I suspect that the MMIC has a problem. Will check to see if I have a 
replacement. Should not be too critical since the frequency is relatively 
low.

>- The EPROM must be faster than the slow old one's. I haven't looked at the 
>specifications but 100 ns should be sufficient fast.
>

Hmm, I will check the EPROM speed marking.

I will try theese things later today.

73 de la9eea
Marius

>
>Old E-Mail 13.12.2001
>
>Hi Doug and all
>
>I have to excuse me. I was much over enthusiastic yesterday when I wrote 
>the e-mail about adding a pull up resistor to PIN 12 of the LMX1501. The 
>truth is that this pull up won't change much.
>The real bug comes from the shift register and LO frequency synthesizer 
>programming. Normally there are 48 bit of data necessary to program all. 
>Sometimes it happens, that only 16 or 32 bits are shifted out from the DSP. 
>If the latch is closed with the wrong data, the synthesizer is programmed 
>the wrong way and the VCO gets unlocked.
>I've changed the DSP program to prevent this and almost everything is 
>performing well. The change is as following:
>Latch data to the sift registers and first LO frequency synthesizer only if 
>there are 3 blocks of 16 bit data shifted out, else don't latch and throw 
>away the data.
>With this change, the PLL is locked as long as I stay within the tuning 
>range. If I leave the tuning range the PLL gets unlocked but locks again 
>when I tune back. The only drawback is that I don't know if the displayed 
>frequency is correct with the hardware frequency. The frequency may be 
>wrong one frequency increment. The next time when a correct tuning 
>increment is shifted out; the VCO frequency catches up the displayed 
>frequency. More research has to be done on this subject.
>73 de HB9OMQ Paul
>
>-----Urspr�ngliche Nachricht-----
>Von:	Marius Hauki [SMTP:[email protected]]
>Gesendet am:	Montag, 5. August 2002 11:03
>An:	[email protected]
>Betreff:	[DSP-10] Problems with DSP10 PLL lock
>
>Hi DSP-10 list members.
>
>I have progeammed the UHF3M21.HEX into a 27c512
>eprom and inserted it (offset) into the eprom socket
>of the EZ-kit since the 27c512 had fewer pins that the
>memory chip that sat there originally.
>
>When I run UHFA.EXE on the PC with the UHF3M21.HEX burnt in the eprom
>I get an error msg  about the filter coefficients and that the filter 
>design
>is not available. When I try to download UHF3.EXE with EZFAST instead, then
>the UHFA software starts to plot data and some data comes up on the 
>spectrum
>analyser display. Then there is at least data transmission between the DSP
>and the PC going on it appears.
>
>I get an error message from UHFA stating that there is a problem with PLL
>lock (E30 PLL UNLOCK). The PC beeps a few times per second as well.
>
>I have hooked on the scope to a few points on the 19.68 MHz VCO signal 
>chain
>and the output signal looks pretty messed up (distorted) after the U8 MMIC.
>Before U8 the signal looks quite clean! I am starting to think that I have
>killed the MMIC. It looks like the white dot is on the correct spot as well
>(white dot = input). The DC voltages look a little strange as well compared
>to what is described in the dsp-10 assembly manual. I measure 5.62 volts DC
>on pin 3 of U8. The voltage is 10V on L29 and R61 is marked with 331 so it
>looks like the resistor has the correct value as well.  I confirmed the
>measurements with the spectrum analyzer. The harmonics is as strong as the
>fundamentals coming out of U8.  The 10 MHz reference is present on both
>plls.
>
>The VHF LO looks quite clean by the way, and the harmonics are down. When I
>look at the LD output from the U7 IC it has pulses on it. The LD output 
>from
>U104 also has pulses on it.
>
>Does pulses on the LD outputs indicate unlock ?
>
>Is there anoyone on the list that has experienced similar problems and can
>give me a few hints ?
>
>73 de LA9EEA
>Marius
>
>
>
>
>
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