Why Cristal don't oscillate??

pinkfloyd11 · Joined: 02 Jul 2007 Posts: 247

Dear Friends

I have realized a program on ATmega8515 and it work good when run on STK500.

After I have realized a prototype on bread board using the same cristal placed on stk500. The pin of cristal are placed between Xtal1 and Xtal2.
From the same pin 2 condenser of 33pF go to gnd.

The clock fuse bit selected is:
Ext. RC Osc. 8MHz - 12 MHz StartUp time : 6CK+4ms

Why I do not view oscillation when place the scope on pin 19?

Thanks

SteveT · Joined: 16 Apr 2005 Posts: 61

Hello,

Check for clean connection without FLUX. I have already this probleme with SOLDER containt WATER SOLUB FLUX. And check for your power supply, to avoid to much ripple on the supply line, The evaluation board have a good filtration....

Steve

ps. You have seen that my English is a bit special, excuse me

Luciano · Joined: 29 Nov 2004 Posts: 3149 Location: Italy

Hi,

Wrong fuse if you use a 8MHz crystal.

AVR Studio 4.13

Use this setting:
Ext. Crystal/Resonator High Freq.; Start-up time: 16K CK + 64 ms

Best regards,

Luciano

pinkfloyd11 · Joined: 02 Jul 2007 Posts: 247

Dear Luciano

I use 16MHz quartz.
In this case which is the best fuse?
Are 33pF correct value?

Thanks

Luciano · Joined: 29 Nov 2004 Posts: 3149 Location: Italy

Hi,

For a 16MHz crystal use this setting:
Ext. Crystal/Resonator High Freq.; Start-up time: 16K CK + 64 ms

Make sure you are using an ATmega8515 and not an ATmega8515L.
Speed Grades:
0 to 8 MHz for ATmega8515L
0 to 16 MHz for ATmega8515

* * *

Click to enlarge the picture

Best regards,

Luciano

pinkfloyd11 · Joined: 02 Jul 2007 Posts: 247

Hello

on chip there is this:

ATMEGA8515
16PU
0602

Howhewer on STK500 I have 16MHz crystal and when the same is placed on it, work good.

Thanks

Luciano · Joined: 29 Nov 2004 Posts: 3149 Location: Italy

Hi,

The crystal is used for the oscillator on the STK500.

When you plug an AVR chip into the sockets of the STK500
the AVR chip gets the TTL clock from the the oscillator on the STK500.
(See the STK500 manual for details).

The second clock option you have while using the STK500 is to
remove the jumper XTAL1 and use the internal RC oscillator of the AVR.

Best regards,

Luciano

pinkfloyd11 · Joined: 02 Jul 2007 Posts: 247

Hello

I have set the fuse bit:

Ext. Crystal/Resonator High Freq.; Start-up time: 16K CK + 64 ms

and now work good also on bread board!

Thanks