AnsweredAssumed Answered

MCG external crystal for usb - s08JM60

Question asked by travrt travrt on Apr 15, 2009
Latest reply on Apr 18, 2009 by travrt travrt

Hello,

 

I have a s08JM60 I am trying to use the usb module on, and one of the requirements is that I have an external clock so I can have a 24Mhz bus clock.  I have app note AN3560 which has code for an external 12Mhz crystal, which is what I have.  But when I run the MCG_Init() it errors out with an ILLEGAL BP.  Once I get this error I can not reconnect to the chip without a reset.  I get an unable to execute command. 

 

Here is the code from the app note.

 


void MCG_Init(){/* the MCG is set to FEI mode by default, it should be change to FBE mode at first */MCGC2 = 0x36;                     /*Select high frequency, high gain, Oscillator requested*/while(!(MCGSC & 0x02));           /*Wait for the stable of Oscillator */MCGC1 = 0x9B;                     /*External clock is selected, RDIV = 0b011 (to get 1.5MHz)*/while((MCGSC & 0x1C) != 0x08);                                  /*Check whether the external reference clock is selected */                                  /* Switch to PBE mode from FBE*/MCGC3 = 0x48;                     /*Enable PLL, VDIV = 0b1000, multiply by 32*/while ((MCGSC & 0x48) != 0x48);   /*Wait for the PLL to be locked */                                  /*Switch to PEE mode from PBE mode*/MCGC1 &= 0x3F;                     /*PLL output is selected*/while((MCGSC & 0x6C) != 0x6C);                                   /*Wait for the PLL output becoming the system clock source */return;}

 

The error starts at either the MCGC1 &= 0x3F;

 

or 

 

while((MCGSC & 0x6C) != 0x6C);

 

Could wrong value capacitors cause this?  It does kick start crystal as I can see a 12Mhz signal on the scope.

 

Travis

 

 

 

Added p/n to subject.

 

 

 

Message Edited by NLFSJ on 2009-04-16 09:17 AM

Outcomes