Mehmet Fide

MC9S08LC60 - Clock monitor questions

Discussion created by Mehmet Fide on Mar 14, 2007
Latest reply on Mar 20, 2007 by Mehmet Fide
Hi,
 
I'm using 32.768Khz external xtal in FEE mode and I've enabled clock monitor.
 
- What will the MCU frequency be if external crystal fails when the MCU is running?
 
- What happens if external crystal fails in stop3 mode? I'm using external crystal in stop3 mode to wake up every second with RTI. Does it automatically wake up at such as failures? What will the MCU frequency be after waking up?
 
- Can I keep the bus frequency approximately constant when external xtal fails? Because my application needs clock based communications such as I2C(100kHz), SPI(400-500kHz) and SCI(9600baud).
 
- In some extreme cases such as temperature and humidity, the external low power crystals may stop. And reworks in normal conditions. Can clock monitor automatically switch to external xtal if it works?
 
- Why doesn't current consumption of the MCU reduce about 9uA indicated in the datasheet when I disabled the clock monitor (LOCD = 1). Disabling or enabling the clock monitor don't change the current at all. May it be not enough that asserting LOCD bit to disable clock monitor?
 
- Does freescale has an application not about clock monitor?
 
 
Code:
// LOLRE Generate an interrupt request on loss of lock.// MFD Multiplication factor(N) = 6// LOCRE Generate an interrupt request on loss of clock.// RFD Division factor(R) = 1// Ficgout = fext * P * N / R ; P=64, N=6, R=1  -> Ficgout = 12.582912 MHz, Fbus = 6.291456 MHzICGC2 = 0b00010000;// HGO Oscillator configured for low power operation.// RANGE Oscillator configured for low frequency range. FLL loop prescale factor P is 64.// REFS Oscillator using crystal or resonator requested.// CLKS FLL engaged, external reference// OSCSTEN Oscillator enabled when ICG is in off mode, CLKS = 1X and REFST = 1.// LOCD Loss of clock detection enabled.ICGC1 = 0b00111110;

 
the MCU is MC9S08LC60.

Regards,
BP.
 
Alban Edit: I fixed my rubbish edit

Message Edited by Alban on 2007-03-14 03:39 PM

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