Good news(?): looking at the TMS4116 (14 out of 16 are from this brand in my board), address setup time before /RAS falling edge is 0 ns, so the address can change right during /RAS edge and must be stable for at least 35ns (assuming the slowest grade) after the falling edge. So my analog scope will catch this easily as the problem can only be if an address toggles after the /RAS falling edge. On Tue, Feb 20, 2018 at 8:24 PM, Francesco Messineo <francesco.messineo@gmail.com> wrote: > On Tue, Feb 20, 2018 at 7:37 PM, Gerrit Heitsch > <gerrit@laosinh.s.bawue.de> wrote: >> On 02/20/2018 07:28 PM, Gerrit Heitsch wrote: >>> > >> >> >> Oh.... If your scope is analog, try to set it to 'chop' instead of >> 'alternate'. The reason for that is that 'alternate' will do a full trace of >> one signal and then a full trace of the other. If you switch to 'chop', it >> will quickly alternate between both inputs while doing the traces. This way >> you get to see what is happening on both inputs at the same time while >> 'alternate' will introduce a lag. With digital signals that will suggest a >> relationship between 2 signals that might not actually be there. > > yes, I already knew that. I routinely use chop mode to look at the > relationship between two digital signals. > Thank you for the /RAS suggestions, it wasn't clear to me that the > corruption could happen only close to /RAS being asserted, > I was also trying to check what was happening before /CAS going low. > One big problem with analog scopes like mine, is that I can't see > what's before the trigger, so if an address line is changing right > before /RAS edge, I won't see it. > I'll see how close is too close for a 4116 anyway, maybe I'm lucky if > I can have a couple of /RAS cycles on the same sweep and still > measure when an address is changing too close (if any). > > Frank Message was sent through the cbm-hackers mailing listReceived on 2018-02-20 20:02:05
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