Hi Peter, > One difference is that the TTL inputs have an RC filter, the differential > inputs have none.
Hmm, that could still point towards a noise issue then. > I wonder if your index outputs can drive the termination resistor. Have you > measured you index and /index outputs for reasonable differential output > voltage when terminated by the 7I29? The outputs swing from 0.48V to 4.1V. It makes no noticeable difference in either TTL or differential modes. > Also are you sure about the jumpering: differntal mode is selectec with > jumper > W1 or W4 moved so its closer to the encoder 10 pin header Yes. At the moment the jumper is away from the header. > Im not sure there are any guarantees of what will happen if one input is > connected to a possibly noisy input line and the other is open. I would not > expect any outputs signal as I would expect the termination resistor to make > the open input follow the noise driven input. According to your 7i33 data sheet you are using a 26LS32 which has a differential voltage sensitivity of 100mV. I disconnected the line at the encoder end (very difficult at the drive end with those IDC headers) so noise pickup on the line could be enough to get past that threshold. The 26LS32 has a built in pull up resistor on one input and a pull down on the other to try to catch a disconnected line. However your terminating resistor is probably swamping the effect of the internal resistors. > Yes, and we've pretty much had 0 trouble with it. Heh. I'm good at breaking things :-) Les ------------------------------------------------------------------------------ Enter the BlackBerry Developer Challenge This is your chance to win up to $100,000 in prizes! For a limited time, vendors submitting new applications to BlackBerry App World(TM) will have the opportunity to enter the BlackBerry Developer Challenge. See full prize details at: http://p.sf.net/sfu/Challenge _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
