topic MCF51CN128 and external clocking voltage level in ColdFire/68K Microcontrollers and Processors https://community.nxp.com/t5/ColdFire-68K-Microcontrollers/MCF51CN128-and-external-clocking-voltage-level/m-p/212290#M10559 <HTML><HEAD></HEAD><BODY><P>I'm a little confused after browsing datasheet and reference manual. I couldn't find information about the voltage level of external clock for the cpu. In my current desigh there are many ICs required clocking, so I decided to use programmable&nbsp; PLL-based synthesizer with multiple outputs, like CDCE925, CDCE949.&nbsp;</P><P>Do I have to use VDD level clock ? I have a lot of experience with ARM based MCUs, and a lot of them require 1.8V level external clock signal. There is no information regarding the external clock voltage level in the datasheets exposed on the web site.</P></BODY></HTML> Mon, 06 Jun 2011 23:15:51 GMT KSlava 2011-06-06T23:15:51Z MCF51CN128 and external clocking voltage level https://community.nxp.com/t5/ColdFire-68K-Microcontrollers/MCF51CN128-and-external-clocking-voltage-level/m-p/212290#M10559 <HTML><HEAD></HEAD><BODY><P>I'm a little confused after browsing datasheet and reference manual. I couldn't find information about the voltage level of external clock for the cpu. In my current desigh there are many ICs required clocking, so I decided to use programmable&nbsp; PLL-based synthesizer with multiple outputs, like CDCE925, CDCE949.&nbsp;</P><P>Do I have to use VDD level clock ? I have a lot of experience with ARM based MCUs, and a lot of them require 1.8V level external clock signal. There is no information regarding the external clock voltage level in the datasheets exposed on the web site.</P></BODY></HTML> Mon, 06 Jun 2011 23:15:51 GMT https://community.nxp.com/t5/ColdFire-68K-Microcontrollers/MCF51CN128-and-external-clocking-voltage-level/m-p/212290#M10559 KSlava 2011-06-06T23:15:51Z Re: MCF51CN128 and external clocking voltage level https://community.nxp.com/t5/ColdFire-68K-Microcontrollers/MCF51CN128-and-external-clocking-voltage-level/m-p/212291#M10560 <HTML><HEAD></HEAD><BODY><P>If you read the Data Sheet there is a specification for all digital inputs.</P><P>&nbsp;</P><P>P Input high&nbsp;voltageall digital inputs</P><P>VIH VDD &gt; 2.7 V &nbsp;0.70 x VDD &nbsp; VDD&nbsp;&gt; 1.8 V &nbsp; 0.85 x VDD&nbsp;</P><P><A href="http://cache.freescale.com/files/32bit/doc/data_sheet/MCF51CN128.pdf?fpsp=1" rel="nofollow" target="_blank">Data Sheet</A></P></BODY></HTML> Tue, 07 Jun 2011 02:51:02 GMT https://community.nxp.com/t5/ColdFire-68K-Microcontrollers/MCF51CN128-and-external-clocking-voltage-level/m-p/212291#M10560 JimDon 2011-06-07T02:51:02Z