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Christian Vogel vogelchr at vogel.cxHi Harald, I've not yet looked at your updated design, just finished the Christmas celebrations with relatives and so on ;-)... > I've meanwhile updated the design > (last night) to actually place two RJ45 sockets, one in TE and one in NT > mode. I would go with the jumper-selectable method, but that's maybe just personal preferance. > The TDN / RDN are not differential signals, if that's what you're > thinking of. Indeed, that's what I thought of, nevertheless I'd try to have at least the clock lines somewhere adjecent to ground, even if it's only based on my gut feeling. >> I don't know about the intended cable lengths, but maybe a few series >> resistors for dampening the signal wouldn't hurt. > You're referring to which signals? SPI and TMS, if you have fast outputs on either the E1 transceiver or the microcontroller/fpga, series resistors (say... 68 Ohm) might dampen the ringing on the edges. > I'm not sure how easy that is, I've already spent a lot of time with the > layout to make sure the autorouter doesn't produce complete crap. So > in order to conserve time, I may not be doing that. I never used the eagle autorouter, because I think it doesn't produce elegant routing, or sometimes no routing at all. Fortunately all my boards were of comparably low complexity (one microcontroller, maybe one or two small additional ICs, everything low pin-count). I'll try my luck on manually routing the new board tomorrow in the morning or so... > I was thinking about a BAV99 (it's used on HFC-E1), but the IDT data > sheet specifically specifies one diode type, and it has very different > characteristics (200mV less forward voltage, ...) than the BAV99. I checked the datasheet and they use rather strong (500mA and up) schottky diodes (hence the lower forward drop compared to the BAV99). Possibly they are considering their product being connected in a commercial telco-equipment with a few kilometres of cable connected to it, and the diodes are for protecting the inputs from overvoltage. Personally, I'd say that for the current design you can easily go with a little weaker diodes, such as the BAT54s (dual in SOT23 smd) which can take up to 200mA (avg). Greetings from bavaria, Chris