Help About Clock initialization in QE128, to set 50MHz

erooll — Mon, 31 Mar 2008 22:26:35 GMT

Hi, I'm trying to use device initialization to setup clock CPU to run at 50 MHz, I use DEMOQE evaluation board, it use a external crystal which value is 32.768KHz, when I put 50 MHz in CPU, a error is generated, shows me that the closer frecuency allows is 29.884416MHz.
Attach the image of settings in device initialization.

Someone could help me with a source code by initialize clock to set CPU clock at 50MHz

Thanks.

Re: Help About Clock initialization in QE128, to set 50MHz

ProcessorExpert — Thu, 24 Apr 2008 15:29:11 GMT

The "Internal bus clock" property refer to the BUSCLK signal on the Figure: 1.3 - System Clock Distribution Diagram in the reference manual of the MCF51QE128. The CPU core clock is twice the Internal bus clock. So to setup the CPU clock to 50MHz the Internal bus clock mus be set to 25MHz. Please note that with the 32.768kHz external crystal the nearest possible value is 25.165824MHz.

Weblink to the reference manual:
http://www.freescale.com/files/32bit/doc/ref_manual/MCF51QE128RM.pdf?fsrch=1

Processor Expert Support Team
www.processorexpert.com

topic Re: Help About Clock initialization in QE128, to set 50MHz in ColdFire/68K Microcontrollers and Processors

Help About Clock initialization in QE128, to set 50MHz

Re: Help About Clock initialization in QE128, to set 50MHz