> 1v across 270K represents 3.7 microamps, which isn't much, particularly > at 25MHz. (I assume that you're using SPI to access the card, but the > observation still holds).
Yup, I'm planning to use the SD card in SPI mode (at least for now). And this line is the CS/CD line, so it's not even running at 25MHz. And as Noel pointed out, this is happening without the SD card even being plugged in. I'm not surprised at cross-talk, I'm surprised that the cross-talk appears so clean. It's not spikes but fairly clean, 1V square pulses. > And if you're using SPI, have you installed > pullups on unused pins? Yup, I put in all the pull-ups. > I'd go to interleaved ground cable or UTP for the device. Also, make > sure that your 3.3V supply is adequately decoupled--an SD card can draw > somewhere n the neighborhood of 100ma when operating, if the datasheets > are to be believed. I use a separate 3.3V LDO regulator at the SD card > socket. Good point. I really should have put a good decoupling cap nearby and the production card should have its own regulator.
