Sorry to bother you all with this, but I'm still having some issues. First off, what are the load cap requirements for the xt2 of msp430, or what document can I find that in? I've not been able to locate it anywhere..
I've been trying to get it to work with this part CSTCE8M00G55Z-R0 (datasheet @ http://www.murata.com/catalog/p16e.pdf -- digikey part 490-1219-1-ND) -- an 8Mhz ceramic resonator with a load capacitance of 30/33/39pF (according to the datasheet -- not sure why it lists three) with the MCU running at 3.3V. Is this out of spec? I'm using a simple example, but it gets stuck in the do while loop... WDTCTL = WDTPW + WDTHOLD; // Stop WDT P3SEL |= 0x30; // P3.4,5 = USART0 TXD/RXD volatile unsigned char j; BCSCTL1 &= ~XT2OFF; // XT2on do { IFG1 &= ~OFIFG; // Clear OSCFault flag for (i = 0xFF; i > 0; i--); // Time for flag to set } while ((IFG1 & OFIFG)); // OSCFault flag still set? is there anything else I can try? Thanks again! Reza wh_fcab wrote: > > Reza, > > Well, both requirements need to be met. Oscillator circuits (such as > those integrated onto the microprocessor die) have certain requirements > for capacitive and resistive feedback and loading, to ensure reliable > start-up and oscillation strength. So does the crystal. It used to be > that you had to design your circuits taking into account the oscillator > and crystal requirements, so indeed it was MCU-specific. Modern > integrated circuits have wide ranges for capacitance (and/or feedback > resistor) requirements, so today the crystal requirements are usually the > determining factors in choosing the load capacitance values. > > I have not played with the 16 MHz version of the chip, so let us know if > you do a design with it. > > William > > P.S.: To the other subscribers on the list: If this thread is getting > too out-of-scope for the list, let us know and we'll take this off-list. > > > thereza wrote: >> William - >> >> Thanks for the excellent information. My only confusion is that my >> adviser >> (I'm a grad student) mentioned that the load capacitance of a crystal has >> to >> be equal to what the MCU expects. I had thought that it didn't matter as >> long as you got the values equal to what the crystal expects. Who was >> right? Or is it MCU specific? >> >> Also, I've noticed that there is a new 16Mhz version of the chip -- have >> you >> had any experience with it or have any opinions about it? >> >> Thanks! > > -- View this message in context: http://www.nabble.com/clock-questions-tf3456545.html#a9745223 Sent from the MSP430 gcc - Users mailing list archive at Nabble.com.
