Quartz crystal not running

[arozm]

Can anybody tell me what do I have to do to make quartz running?

 

[Nigel Goodwin]

Can anybody tell me what do I have to do to make quartz running?

You need to connect it as part of an oscillator circuit - the exact way can vary greatly, and is highly dependent on the application it's intended for.

You need to give much more information!.

 

[arozm]

It's connected to clk+ and clk- to the National LMX9820 the way it should be, I've got another one running, which is connected the same way.
It has 2.2 V and ground. What else it needs to run?

 

[Nigel Goodwin]

It's connected to clk+ and clk- to the National LMX9820 the way it should be, I've got another one running, which is connected the same way.
It has 2.2 V and ground. What else it needs to run?

I don't know anything about an LMX9820, but on a PIC you have to program the processor to tell it the type of oscillator in use - does this require something similar?.

Also, how are you checking for oscillation?, if using a scope you need to use a x10 probe - otherwise the scope capacitance usually stops the oscillator.

Bear in mind faulty crystals are fairly common, I probably replace one every few months in TV's etc.

 

[Russlk]

I see from the data sheet that it is a 32kHz crystal. I have tried several circuits and several crystals and have not had any work, so tho I can't help you, I can comiserate. One Mhz and up crystals work OK but 32 kHz don't work, I don't know why.

 

[Nigel Goodwin]

One Mhz and up crystals work OK but 32 kHz don't work, I don't know why.

Again I can only quote from PIC's, a PIC has three different settings for crystal oscillators - LP, XT, and HS. LP is for 32KHz crystals, XT for medium frequencies (upto 10MHz or so), and HS for high speed crystals (over 10MHz).

As MicroChip obviously spend time and money designing their chips like this, it's seems reasonable that a single circuit isn't likely to work well over a huge range of frequencies.

Are there any settings on the chip in question?.

 

[Sebi]

The cheap miniature clock Xtals have very low Q.
Most of case help this circuit.

 

[Roff]

Guys, I think you missed something. According to the **broken link removed**, the main synthesizer clock crystal is 10 - 26MHz. This **broken link removed** calls out a 12MHz crystal. The 32kHz crystal is for an optional low power mode, and apparently has a dedicated set of pins.

 

[SGReal]

Ron H was right, the 32khz pins must not be connected. Use the 12Mhz clk pins with 12Mhz crystal.

Anyway I am about to use an LMX9820 also, Nigel mentioned: "I've got another one running, which is connected the same way. " - do you mean you have an LMX9820 working? If so pleast tell me cause I would have some questions because I am stucked in powering up a transparent BT serial connect with this...
(IF anyone knows is pls reply)

The facts and suggested solutions of problem:
Built circuit:
1. I have LMX powered properly 3.3V
2. I have a pure 40 mm length wire as antenna just for testing period (an other module worked fine using this)
3. The 12Mhz crystal was tried with 2x10pF, 2x12pF, 2x8.2pF and other capacitors.

Suggestions:
1. the LMX9820 automatically after booting up is discoverable
2. and automatically responses to discoveries (eg. from PDA)
3. and automatically establishes connection offering serial port profile

Problems:
1. I cannot discover it using my PDA
2. The HostWU is blinking just after bootup, but found nowhere that LÉMX should do that
3. (this is partially at the moment) the UART is connected to a microcontrollet (PIC) and the LMX saqys 0x00 0x08 after every reset - what is weird also

Suggestions for problem solution:
1. I think that the crystal and capacitors (the figure showed that above) a properly working togethet to be in the required 15-20 ppm - How sholud I select proper setting?
2. Next thing what can be weak is the antenna: should I use some elements to connect the antena? (eg capacitor)
3. for the HOSTWU and UART messages I dont even have idea... if anyone knows something please post it.

Thanks

 

[Nigel Goodwin]

Anyway I am about to use an LMX9820 also, Nigel mentioned: "I've got another one running, which is connected the same way. " - do you mean you have an LMX9820 working?

No, my posts refer to PIC's, I've never seen an LMX9820, and don't even know what one is.