Problem found! Thank you for the comments and suggestions. The board supports multiple levels of output (RS-232, RS-422, etc) on the SCC ports, controlled by Port B pins. I had initialized the pbpar/pbdir backwards for these pins.
> -----Original Message----- > From: Brown, David (dbrown03) [mailto:DBrown03 at harris.com] > Sent: Friday, May 05, 2000 10:17 AM > To: linuxppc-embedded at lists.linuxppc.org > Subject: interference between scc serial and ethernet: more > information > > > > The target is a custom board similar to the EST8XX > configuration, with an > 860 and an LXT908 PHY. I ultimately need to run PPP on SCC3. > When ethernet > receives data, it messes up SCC3's configuration somehow. I > briefly tested > with SCC2 and saw the same thing, but I have concentrated on SCC3. > > It's a 50MHz MPC860, identified by 8xxrom as XPC860xxZPnnC1 > and actually > stamped as XPC860ENCZP50C1. Running at 50MHz. > > Three nodes on the ethernet: the target, the Abatron BDI2000, and the > development host. > > Case 1) Linux boots with default parameters, no IP address. > I use SCC3 > serial, no problem. Then, on the development host, I ping a > non-existent > address (causing an ARP request broadcast). After that, the > SCC3 serial is > not working. Sometimes, when I write to SCC3, garbled > characters come out > (like it's the wrong baud rate). Other times, nothing comes > out at all. > > Case 2) Linux boots with IP address parameters. I use SCC3 serial, no > problem. Then, on the target, I ping a non-existent address. > Serial still > works fine. I get "neighbour table overflow" messages. > > Case 3) In enet.c, in cpm_enet_rx(), I commented out code so that all > received frames get tossed. Again, SCC3 serial stops working when the > development host pings an unknown address. > > I tried activating kgdb to debug this, but kgdb stops working > as soon as the > init shell starts. It seems to be a fight over which process > gets the input > data. I'm looking at it with BDM, but that's quite slow > since I have to > translate memory references. > > I see four potential possibilities. > a) A bug in the enet or serial driver. Not likely, since > others report that > Ethernet and SCC serial ports work simultaneously for them. > b) A hardware problem on my board. My co-worker says that's > unlikely, since > his low-level test software exercises Ethernet RX and uses SCC3 as the > console. > c) A blatant configuration error in my setup of Linux. Not > likely, since > Ethernet and Serial each work independently. > d) My board violates some assumptions made by Linux and/or > the drivers. > That seems to me to be the most probable, but I can't think > of what it might > be. > > Please feel free to throw out random ideas as to what I > should look for. > ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
