ColdFire/68K Microcontrollers and ProcessorsのトピックRe: Crystals 48MHz that works on MCF52259 ?

Crystals 48MHz that works on MCF52259 ?

YodaC — Thu, 17 Jun 2010 21:50:58 GMT

Hello,

I make a new design for MCF 52259 with a common HC49 crystal of 48MHz.
But the crystal oscillate @16Mhz.
I tried to change crystal and values of caps and resitors without success.
The only way is to take the crystal from the tower. (TWR-MCF5225X)

Could you give me a list of crystals that works on MCF52259 please ?

Thank you.

Re: Crystals 48MHz that works on MCF52259 ?

Nouchi — Thu, 17 Jun 2010 22:12:08 GMT

Hello,

Because you use a 48Mhz crystal on 3rd overtone, you need a 48Mhz crystal working on fundamental frequency.

You can have a look to the M52259DEMOMCU board BOM, this board use a discountinued Citizen parts, replacments (given by Citizen) are TXC-7A , ABM7 and maybe others, but remember it should work on fundamental, not on overtones.

Emmanuel

Re: Crystals 48MHz that works on MCF52259 ?

YodaC — Thu, 17 Jun 2010 23:01:55 GMT

Thank you for your fast answer and your explanations

Re: Crystals 48MHz that works on MCF52259 ?

pgo — Fri, 18 Jun 2010 11:38:57 GMT

Dear YodaC,

Just an extra note - the 48MHz ABM7 crystal is 3rd overtone by default - You need to specify the fundamental mode operation when ordering. This may be true of the other one. (Just to re-enforce what BugMan said!)

e.g. ABM7-48.000MHZ-D2Y-F-T (The 'F' is important!)

bye

Re: Crystals 48MHz that works on MCF52259 ?

Kopone — Mon, 25 Oct 2010 21:09:43 GMT

I just had the very same problem with my 52259 project.

Since 48MHz oscillators seem to be much more easily available anywhere, I am willing to switch to these now.

I just never used one before. Is it that I simply apply power (+100nF) to the oscillator and feed the output to EXTAL?

So I'd only leave my 10k pullup connected to XTAL and also the code to switch to external clock wouldnt change? (I couldnt find any register in the RM that would make a difference between external crystal or oscillator).

I'd happily appreciate any confirmation (or correction) on that.

Thanks,

Sven

Re: Crystals 48MHz that works on MCF52259 ?

TomE — Tue, 26 Oct 2010 11:10:14 GMT

Table 7-14. OCLR Field

Table 7-14. OCLR Field Descriptions

6 Reference Source bit. This bit configures the external oscillator for operation with an external crystal or
REFS external oscillator.
0 External oscillator is running in external oscillator mode.

1 External oscillator is running in external crystal mode.

Re: Crystals 48MHz that works on MCF52259 ?

Kopone — Tue, 26 Oct 2010 19:27:55 GMT

Thanks a bunch, totally missed that one!

Sven