Dear all Maybe somebody can help me a suggest me what I have to do dealing with the problem I desribe below: I have to build a PCB board in which I have to interconnect a 5V TTL device with a 3.3V TTL one. From the 5V device goes a bus of 9 lines to the inputs of the 3.3V device, which is not 5V tolerant. The speed of the signals is 80 MHz, but the potential problem I have is with the rise time of the signals which I guess is about 1ns (I don`t have the device in my hands yet), and the bus length will probably be more than 7cm, so I'll have to work with the connections as they were transmission lines. How should I interconnect the devices in order to keep the integrity of the signal? Lets suppose that the impedance that I implement for the line is 50 Ohm, should I use a voltage divider in the source (ie, in the 5V device) or in the end? and what values for the resistors in order to match the impedance of the line? Or should I do someting completely different? Thaks in advance ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu