S12 / MagniV Microcontrollers中的主题 pull up/down recommendation for external data bus of S12 https://community.nxp.com/t5/S12-MagniV-Microcontrollers/pull-up-down-recommendation-for-external-data-bus-of-S12/m-p/671292#M14105 <HTML><HEAD></HEAD><BODY><P>Dear all,</P><P></P><P>we are operating a MC9S12XDP512 / MC9S12XEP100 micro controller in expanded mode. On the external bus a static RAM IC is connected without external pull up / down resistors on data bus.</P><P>What is your the recommendation regarding pull up / down resistors:</P><UL><LI>do we need pull up or pull down at all on the external data bus to have a defined signal level in case the external static RAM IC is not accessed?</LI><LI>should / can we make use of the internal pull up feature of PORT C / D to have defined signal levels on the external data bus (set PUPDE PUPCE in PUCR register)?</LI><LI>should we better use external pull up / down resistor to have defined signal levels on the external data bus?</LI><LI>is there an application note about this topic and where do we find it?</LI></UL><P></P><P>We are looking forward to get an answer to the questions soon.</P><P></P><P></P><P>With kind regards</P><P>Leopold</P></BODY></HTML> Mon, 08 May 2017 15:13:28 GMT leopoldgemsch 2017-05-08T15:13:28Z pull up/down recommendation for external data bus of S12 https://community.nxp.com/t5/S12-MagniV-Microcontrollers/pull-up-down-recommendation-for-external-data-bus-of-S12/m-p/671292#M14105 <HTML><HEAD></HEAD><BODY><P>Dear all,</P><P></P><P>we are operating a MC9S12XDP512 / MC9S12XEP100 micro controller in expanded mode. On the external bus a static RAM IC is connected without external pull up / down resistors on data bus.</P><P>What is your the recommendation regarding pull up / down resistors:</P><UL><LI>do we need pull up or pull down at all on the external data bus to have a defined signal level in case the external static RAM IC is not accessed?</LI><LI>should / can we make use of the internal pull up feature of PORT C / D to have defined signal levels on the external data bus (set PUPDE PUPCE in PUCR register)?</LI><LI>should we better use external pull up / down resistor to have defined signal levels on the external data bus?</LI><LI>is there an application note about this topic and where do we find it?</LI></UL><P></P><P>We are looking forward to get an answer to the questions soon.</P><P></P><P></P><P>With kind regards</P><P>Leopold</P></BODY></HTML> Mon, 08 May 2017 15:13:28 GMT https://community.nxp.com/t5/S12-MagniV-Microcontrollers/pull-up-down-recommendation-for-external-data-bus-of-S12/m-p/671292#M14105 leopoldgemsch 2017-05-08T15:13:28Z Re: pull up/down recommendation for external data bus of S12 https://community.nxp.com/t5/S12-MagniV-Microcontrollers/pull-up-down-recommendation-for-external-data-bus-of-S12/m-p/671293#M14106 <HTML><HEAD></HEAD><BODY><P>Hi,</P><P>a) as a first step I would like to direct you to my supporting material:</P><P><A href="https://community.nxp.com/docs/DOC-93594">https://community.nxp.com/docs/DOC-93594</A> </P><P>Please read it carefully. It will simplify your design and debugging issues.</P><P></P><P>b) No there is no reason to have any pull resistor on the bus.</P><P></P><P>If you have any additional questions, do not hesitate to ask....</P><P></P><P>Best regards,</P><P>Ladislav</P></BODY></HTML> Tue, 09 May 2017 08:33:49 GMT https://community.nxp.com/t5/S12-MagniV-Microcontrollers/pull-up-down-recommendation-for-external-data-bus-of-S12/m-p/671293#M14106 lama 2017-05-09T08:33:49Z