topic Re: 9S08AC60 external ceramic resonator not locking in 8-bit Microcontrollers

9S08AC60 external ceramic resonator not locking

barrygordon — Tue, 09 Apr 2013 22:06:04 GMT

I have built two boards both with a 4Mhz Ceramic Resonator. Both board, using the Cyclone Pro can be programmed and single step.

On one board the ceramic resonator is not locking (using a scope - no oscillator on either pin). The code is set up as in example 2 of the manual. The code is stuck on the while loop.

The ceramic resonator has the bypass capacitors and resistors embedded in the body.

ICGC1 = 0x30;

ICGC2 = 0x30;

/* Wait for LOCK bit */

while (!ICGS1_LOCK);

The circuit ohms out Ok.

Any trouble hints on what to do next.

Re: 9S08AC60 external ceramic resonator not locking

admin — Thu, 11 Apr 2013 00:23:22 GMT

Mistyped when I enter the code:

ICGC1 = 0x78;

ICGC2 = 0x30;

Re: 9S08AC60 external ceramic resonator not locking

bigmac — Thu, 11 Apr 2013 01:14:48 GMT

Hello,

To confirm that the ceramic resonator actually contains embedded resistance, the quiescent voltage measured at each of the pins should be approximately equal at one half Vdd. The oscilloscope probe setting will need to be x10 for 10M ohm input resistance. If the two voltages significantly differ from each other, with voltages close to either supply rail, the particular resonator may not contain sufficiently low embedded resistance. I would expect a value of about 1M ohm.

If the capacitance ot the oscilloscope probe is too high, it is possible for the measurement process to cause oscillations to cease. Check for oscillation at both pins.

Regards,

Mac

Re: 9S08AC60 external ceramic resonator not locking

barrygordon — Fri, 12 Apr 2013 01:10:46 GMT

The voltage was the same on each side approx 1/2 Vdd. My scope probes are x10.

I changed out the resonator with a spare and that fixed the problem.

after rechecking the resonator again, it appeared that there was no embedded resistor - I added a 1 meg ohm resistor - that fixed the problem - built 7 modules and all work.