Crystal on c-3024

[Sazabi]

Sorry for maybe such a foolish question, but I can't find answer anywhere else:
i got olimex header board for atmega128.

http://www.olimex.com/dev/avr-h128.html

It has build in jtag and icsp ports for programming. It has also 2 crystals, one is 16.000 and another one is 32768.
What for these 2 are? for programing?
As in spec:
16MHz scillator circuit
32768 Hz oscillator circuit
what is that?
To use it for making c-3024 copy i need to change crystal or add another one?
I plan to program via icsp port, so i guess i don't need one with 16.000?
Thank you!

[i-Bot]

You should remove both crystals, and replace the 16MHz crystal with one of 7.3728MHz to use the C3024 code.

[Sazabi]

Thanks for answer!
But i won't be able to use build in port to program chip if i remove crystals?

[i-Bot]

Once you have installed the 7.3728Mhz crystal, the ISP and JTAG will work fine.

[Sazabi]

why than they have 2 crystals there if one (32768) doesn't affect work?

[i-Bot]

The main oscillator is the 16Mhz and must be present. This can be changed to 7.3728 without a problem. The 32.768KHz oscillator is optional and sometimes used as a real time clock. The C3024 code does not use this, and uses the pins for other purposes.

[Sazabi]

Thanks for help! I should really learn all that stuff about microcontrollers:D

Shame on me, now I know what they used for.