Hi, I tried to replicate the measures of Brian end at the following link you can find my oscilloscope screenshot:
https://photos.app.goo.gl/n39TcOt24QtVrfJo1 The first 16 images are the AD0-AD7 and A8-A15 As you can see I don't have any stuck condition at the outputs of the 8085, now i'll verify the buffers and demultiplexers. Image 17 CLK pin 37 of the 8085 and Image 18 Pin 7 of the 8085 The last 6 images are the most interesting. Here I'm acquiring: CH1) ROM CS CH2) 8085 AD0 CH3) 8085 IO/M CH4) 8085 Reset Out (actually after the buffer) As you can see as soon as I release the reset button, ROM CS and 8085 AD0 start moving but IO/M stay low for ~300ms At this point the ROM CS change completely and from a stady clock, become like a data line. AD0 keep changing and IO/M toggle only 5 times. On the last 3 pictures you can see that this sequence continue exactly the same over and over every ~300ms Brian: Can you please measure this 4 signals in the working unit? I'm doing a single capture, triggering on the falling edge of the reset (CH4). I hope to be closer to find the culprit :) Mauro On Dec 18, 2017, at 6:57 PM, Brian White wrote: > Ah yeah I forgot to relabel a17. I just went one pin too far and mis-labeled > it. I'm not looking at the pdf now, but the a17 pic will be for pin 28 > whatever that is. > > Thank you I'll look at m21. > -- > bkw > > > On Dec 18, 2017 11:54 AM, "Fugu ME100" <[email protected]> wrote: > Are BAD M100 A16 & BAD M100 A17 correctly titled on the screenshots? > > The sawtooth will be caused by the multiplex nature of the bus from AD0-AD7. > > The stuck condition of the lines could just be that the CPU never gets out of > a certain address range so the lines appear never to move. Or it could be > the 80C85 (M19) is indeed bad or the H244 (M21) is possibly bad causing the > inputs to be stuck high. The bad Address lines go straight into M21 based > on the schematic. > > On the bad M100 the pattern repeats ~53ms so that is about 10,000 > instructions (if my math is right) so I would expect all the Address/Data > lines to at least toggle. It looks like M19 is bad. Any other lines appear > to be stuck? > > From: M100 <[email protected]> on behalf of Brian White > <[email protected]> > Reply-To: <[email protected]> > Date: Monday, December 18, 2017 at 5:18 AM > To: <[email protected]> > Subject: Re: [M100] diagnose > > Last night I did a little more poking. > > First, I looked at all the data lines at the cpu on a good M100, and verified > that on a good M100, all of those pins show continuous streams of data while > the machine is on. > > Then on the bad M100 I saw 2 differences from the good M100. > > 1) I can't get a stable trigger lock on any of the A* & AD* pins on the good > M100. > IE, On the good machine the data doesn't repeat exactly around 53ms like it > does on most pins on the bad M100. > > 2) 4 pins are stuck high: A10, A12, A13, A14 > > Screenshots of pins AD0-AD7 & A8-A16 > https://photos.app.goo.gl/vcTg4yUhvjXKBxeh1 > > I thought those ramps and 2-volt sawtooths on the AD0-AD7 lines looked bad, > but the good machine has the same thing. > > -- > bkw > > On Fri, Dec 15, 2017 at 7:52 AM, <[email protected]> wrote: > I have a really basic one like this, based on the Cypress CY7C68013A > https://sigrok.org/wiki/Lcsoft_Mini_Board > > I like to use it with the saleae software, but to have 16ch instead of 8 I > use Sigrok. > > Mauro > > > > Il 15.12.2017 12:56 Brian White ha scritto: > >> On Dec 15, 2017 6:16 AM, <[email protected]> wrote: >> >> BTW: Brian do you have a LA so we can compare the same signals on the ROM >> and RAM addressing/enabling on the working and not working >> Sorry I am looking at them but hadn't picked one yet. >> -- >> bkw > > > > Con Mobile Open 7 GB a 9 euro/4 sett navighi veloce con 7 GB di Internet e > hai 200 minuti ed SMS a 12 cent. Passa a Tiscali Mobile! > http://tisca.li/OPEN7GBFirma > > >
