1. Home
  2. Embedded Programming
  3. cs8900a always returning 0x5555

cs8900a always returning 0x5555

Dear all

I'm trying to use a CS8900a ethernet controller in one of my designs. I connected it to the CPU according to the app notes (16 bit IO mode, CPU's /CS conneced to AEN and /SBHE, I try to use IO mode). I tripple checked everything against the checklist in the app note an83-3 and so far everything looks ok. Hooking up a logic analyzer showes that timeings are ok also. When I plug in a 10BaseT cable from the RJ-45 on my board, the LINK-LED on both sides light. But when i try to read the signature from the register IOBASE+OAh, i always get 0x5555. In fact, i only get the value 0x5555 for all addresses between 0x300 and 0x30e.

I'm now struggling with this problem for days and would really apreciate any help on this. I searched the net and found an old thread about the same issue, but there was no solution to the problem posted. I'm currently realy out of ideas, so any hints on what to check etc. are welcome.

TIA

Markus

Reply to
Markus Zingg
Loading thread data ...

so

Well, we didn't think it was timing because you assured us that it wasn't. :-)

Good work finding the bug!!

Reply to
Gary Kato

You are of course right here. What I was lookign fore (since I consider myself being a beginner) were some general tips/hints what else to check. After this post I did the folowing things

- solder out the oszilator. The lan link went away which for me was some indication that the osizlator seemed to do it's work.

- Used a scope to check the oscilaotor oszilating. It did, but I heard that due to the capacitance of the probe it could oszilate during measure and not before and after. Anyways, I then concluded that the oscilator most likely woule work.

- replaced the cs8900a with aother one. Since this gave the same results, and since the wireing was ok not much more other than the timeing (IMHO) was left over.

I probably would have expected from the experts some advice like well, what you describe leaves open 1) a malfuncitoning chip, 2) oszilator not working or 3) you are worng with your asumptions or 4) any other advice. Being a newbee, one soon feels sort of trapped from such a situation if no one answers. In general I'm keen to learn and even if an advice would not have hit the nail it surely would have helped learning. Not geting a single reply in such a crisis (sorry but to me it was sort of) just makes you feel dumb / even more lost if other questions around your own post are answered within minutes.

Yeah, you have no idea how lucky I am now. The hardware design for this project is now complete and I'm now happy to complete the firmware.

Many thanks for your reply. It's highly apreciated! :-)

Markus

Reply to
Markus Zingg

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.