50MHz resonator
loojade
Posts: 30
Hallo everybody,
Still my experience on SX very low so... I did a application with SX28 using internal clock (4MHz); everything work well. Now I would like to test the system with external clock 50MHz to improve the response of the system.
This are the questions:
- Is the 50MHz resonator marked 500Q ???
- 50 MHz resonator has 3 pin. the midle one must connected to GND and the side pins to OSC1 and OSC2... right???
- between OSC1 and OSC2 is it necessary a 10Kohm resistor?
- Is the correct DEVICE code line the following???
Before with internal clock I used the following:
Must I set any thing in SX-Key before program SX chip???
Thanks in advance for your help
Loojade
Still my experience on SX very low so... I did a application with SX28 using internal clock (4MHz); everything work well. Now I would like to test the system with external clock 50MHz to improve the response of the system.
This are the questions:
- Is the 50MHz resonator marked 500Q ???
- 50 MHz resonator has 3 pin. the midle one must connected to GND and the side pins to OSC1 and OSC2... right???
- between OSC1 and OSC2 is it necessary a 10Kohm resistor?
- Is the correct DEVICE code line the following???
DEVICE SX28, OSCHS2, TURBO, STACKX, OPTIONX FREQ 50_000_000, 45_000_000
Before with internal clock I used the following:
DEVICE SX28, OSC4MHZ, TURBO, STACKX, OPTIONX FREQ 4_000_000, 3_600_000 IRC_CAL IRC_4MHZ
Must I set any thing in SX-Key before program SX chip???
Thanks in advance for your help
Loojade
Comments
Yes the resonator has 3 pins and the middle one is ground. I went to a local electronics store and bought what I thought were resonators, but were actually small bandpass notch filters.
If you got that from Parallax, it is definitely a resonator. It won't hurt to try it.
I am not sure about the marking, but you can search the web for manufacturers that will explain what the code means. It certainly seems to be in the ball park.
Try Google for '500Q 50Mhz resonator' and see what comes up. No resistor is usually needed with the resonator. Generally, a crystal is more likely to require the additonal resistor.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
PLEASE CONSIDER the following:
Do you want a quickly operational black box solution or the knowledge included therein?······
Although not an authoritative answer... I have never used one with a resonator. (Check the datasheet if you want to be sure.)
The settings look good to me although from some old code I just pulled up it looks like I used OSCHS1 for a 50MHz resonator in a previous project.
The only thing that comes to mind is that while you can program the SX with a resonator connected, you can not use the debugger to examine your code with a resonator in place.
NOTE: If you were using a crystal instead of a resonator you should definitely disconnect it before programming!
Also, I think it makes a lot of sense to include the device and frequency settings directly in your program as this eliminates one frustrating step later when you return to old code after working on another project and forget to adjust the settings back properly. Including them in the code ensures they are set or changed properly for each program you load!
- Sparks
Regarding the need of a resistor [noparse][[/noparse]internal or external]. I ran this down in the past and if the SX oscillates in a stable fashion and at the right frequency, one· generally may not be needed.· If the resistor is included and the Sx oscillates in a stable fashion and at the right frequency, that's okay too.
Resonators and crystal come in a lot of different parameters. Some resonators even include the resistor internally.· So I just use a 'rule of thumb' that I leave it out on the resonator and include it with a crystal.
If you were to go into producing 10,000 boards of one design, I would strongly advise you allow for a resistor on your board design as different resonators and crystals might require you include one. Also, the value of the resistor can vary quite a bit, up to 1 meg.
If you really want to design this part of the circuit to be near perfect, you need to test your crystals and resonators for each batch you buy. Bean seems to work at a place that has such a device, but it cost about $10,000USD.
So, it all comes back to a bit of guess work. Once you have stable oscillation in one setting, you can reduce the power to the oscillator until it becomes unstable then return to the next higher setting [noparse][[/noparse]which is confirmed stable]. The oscillator is a big part of the power consumption of the SXes. And the higher the frequency use, the more power is required. So the frequency settings in DEVICE·have a correlation to how much power is being fed into the oscillator circuit.
I don't think having the resistor improperly in or out will ever cause damage to an SX.· But, the SX might not clock or with higher frequency crystals might clock the wrong harmonic frequency.· Having the configuration working but somewhat incorrect is just likely to use more power and in some cases [noparse][[/noparse]50mhz and higher]·generate more EMFI.
Between Senix documents, Ubicom documents, and Parallax documents; you are never going to find one consistent answer.· Points of view and presentations evolved.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
PLEASE CONSIDER the following:
Do you want a quickly operational black box solution or the knowledge included therein?······
Post Edited (Kramer) : 3/22/2008 7:54:19 AM GMT
It is not the oscillator directly that causes the SX power consumption - it is the SX itself. The higher its clock frequency is (no matter if generated by its internal clock driver and an external reosnator/xtal, or an external clock soure), the higher the power consumption is.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Greetings from Germany,
G