external crystal

yogendra agarwal

Prodigy 150 points

Other Parts Discussed in Thread: MSP430F47197

how can i use 8 MHz crystal in MSP430x4197?

now i am using internal clock....... and i can see 6 MHz at MCLK on micro........

over 14 years ago

0 Joerg Quinten over 14 years ago

Guru 17650 points

Hi yogendra,

are you talking about MSP430F47197 (since I don't know an MSP430x4197)?

You can connect the 8MHz crystal to XT2 (XT2IN / XT2OUT terminals). An example initalization code is 'msp430x471x7_hfxt2.c' which is part of the device example codes http://www.ti.com/litv/zip/slac282a

Rgds
aBUGSworstnightmare

0 yogendra agarwal over 14 years ago in reply to Joerg Quinten

Prodigy 150 points

yes, u r right this is MSP430F47197,

can we directly connect 8 MHz crystal to XIN & XOUT pin of micro??????

if yes then give me any example code.

thanks & regards

0 yogendra agarwal over 14 years ago in reply to yogendra agarwal

Prodigy 150 points

any one tell me plz

0 Jens-Michael Gross over 14 years ago in reply to yogendra agarwal

Guru 227245 points

yogendra agarwal said:
if yes then give me any example code.

See the post above yours. The link to the examples is there.

yogendra agarwal said:
can we directly connect 8 MHz crystal to XIN & XOUT pin of micro??????

You can. But you also need to provide the necessary load capacitance (see crystal datasheet, usually two capacitors in the range of 20..33pF each, connected from each pin of the crystal to GND).

0 Alex McLain over 14 years ago in reply to Jens-Michael Gross

Prodigy 110 points

Take a look at chapter 5 of the MSP430x4xx Family User's Guide. It shows the block diagram and registers for the high frequency oscillator, and provides a description of how it works.

Having used 8MHz crystals in MSP430x1xx devices, I can say that it's a pretty easy process once you understand how it works. Flip on the crystal oscillator, wait for it to stabilize, then switch over MCLK (and optionally SMCLK) to source their signals from the crystal instead of the DCO. In my opinion, looking at example code almost makes the process more confusing than just looking at the module's block diagram.

0 yogendra agarwal over 14 years ago in reply to Alex McLain

Prodigy 150 points

i m using 8 MHz crystal with 33pf at XIN & XOUT as per your suggestion....... i have written the following program...... still i am not getting MCLK of 8 MHz.... instead of 8MHz i am getting 6.3MHz at MCLK pin....

SCFQCTL = SCFQ_M;
FLL_CTL0 = XTS_FLL;
FLL_CTL1 = SELM0 + SELM1 + SMCLKOFF + XT2OFF;
SCFI0 = FN_8;

plz suggest.....

thanks & regards

0 Jens-Michael Gross over 14 years ago in reply to yogendra agarwal

Guru 227245 points

yogendra agarwal said:
SCFQCTL = SCFQ_M
SCFI0 = FN_8;

The SCF registers only belong to the DCO/FLL. If usign a crystal, tehy are meaningless.

yogendra agarwal said:
FLL_CTL1 = SELM0 + SELM1 + SMCLKOFF + XT2OFF;

This sets the MCLK to (HF)XT1, if the crystal is running, which it isn't (causing MCLK to fallback to DCO).
And it isn't running because you didn't read the datasheet:
fXT1 XT1 oscillator crystal frequency 0.45..6 MHz
the important part being '6MHz'. HFXT1 doesn't support 8 MHz crystals. (I must admit, this surprises me too, as all other MSPs usually either support no HF crystal on XT1 or maximum CPU speed.

So to attach an 8MHz crystal, you'll need to attach it to XT2, program MCLK to use XT2 (don't set XT2OFF!) and then wait for the crystal coming online (by checking XT2OF bit in FLL_CTL0)

0 yogendra agarwal over 14 years ago in reply to Jens-Michael Gross

Prodigy 150 points

plz provide me exact code for crystal (8MHz) on XT2, for which i can see 8 MHZ pluse on MCLK pin.

plz suggest

thanks and regards

0 yogendra agarwal over 14 years ago in reply to yogendra agarwal

Prodigy 150 points

anyone can tell me plz

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