On 2012-10-07, at 14:34, Gerrit Heitsch wrote: > On 10/07/2012 01:31 PM, silverdr@wfmh.org.pl wrote: >> >> Something is really strangely off / on the verge of specs here. Any help ideas? >> >> Thinking aloud as I don't have a scope here at hand to verify.. could it be that PLA's outputs are not fully compatible with the LS inputs? When sinking off the original ROMs there are no pullups nor anything else on the way. Maybe we need something when connecting those outputs to the LS? > > No, then there is a 74LS139 connected to one of the PLA outputs and that doesn't give any trouble. Yes, it is indeed very unlikely that the _CS lines would be different.. > The vertical bars are indeed strange. Especially since they only happen in the border area where the Char-ROM is not involved in any way. No, I don't think it is a hardware side-effect. I think it is a "signature" left by the programmer that when something goes wrong it displays a sort of uncommon picture using mid-rasterline changes. Maybe it (position / colours - sometimes yellow and black revers and seem to be in different position) even tells something to someone who knows. Like the cryptic digits/"stack" stuff. > Did you remember to put the pullups where they belong so that no input of the LS00 or LS11 is ever floating, no matter what your switches are set to? Yes, I checked it. Shall double-check once more but I believe everything is in place. > Also, did you remember to include 100nF ceramic capacitors between GND and Vcc for the LS? Yes, two small decouplers (104) are in place. I may exchange them but I find it unlikely that they are bad. -- SD! Message was sent through the cbm-hackers mailing listReceived on 2012-10-07 15:00:08
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