Different SHIFTER versions

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czietz
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Re: Different SHIFTER versions

Postby czietz » Tue Jul 10, 2018 6:02 pm

ijor wrote:In this case the bands are more clear, those are not just glitches. I believe however that the cause is very different on the IMP Shifter than on the -38 (or -20) one. It would be interesting to see if adding the diode at the VCC pin fixes the problem. I suspect it might.


Sorry, it doesn't. So, (given that my TT is sadly down for repair) today I had some time to play with my IMP STfm. I confirmed that by default there is no diode between +5V and the Shifter's Vcc pin -- I measure 5 V on the IMP Shifter. Then I added the diode, dropping the Vcc of the IMP Shifter to approx. 4.4 V. However the artifacts in "Let's Do The Twist Again" are still present. Also, I retested the SNDH Update Demo, where I had previously noticed artifacts with the IMP Shifter. They are still present as well at 4.4 V.

Anything else you want to have tested?

I will repeat the test with the -20 Shifter now. And after that, maybe already tomorrow, I can do the measurements on the IMP Shifter (without diode) you asked for.

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Re: Different SHIFTER versions

Postby czietz » Tue Jul 10, 2018 6:17 pm

And this is a screen capture for "Let's Do The Twist Again" with the -20 Shifter -- artifacts as expected:

IMG_2964.JPG
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Re: Different SHIFTER versions

Postby ijor » Wed Jul 11, 2018 2:16 pm

czietz wrote:Sorry, it doesn't. So, (given that my TT is sadly down for repair) today I had some time to play with my IMP STfm. I confirmed that by default there is no diode between +5V and the Shifter's Vcc pin -- I measure 5 V on the IMP Shifter. Then I added the diode, dropping the Vcc of the IMP Shifter to approx. 4.4 V. However the artifacts in "Let's Do The Twist Again" are still present. Also, I retested the SNDH Update Demo, where I had previously noticed artifacts with the IMP Shifter. They are still present as well at 4.4 V.


Interesting. I think I have a pretty good idea about the incompatibility with the older SHIFTER versions (-20 and -38). But not so sure yet about what's happening with the IMP part. Let's wait to see the traces, they might give us some clues.

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Re: Different SHIFTER versions

Postby czietz » Wed Jul 11, 2018 6:22 pm

These are the LA traces with the IMP Shifter (as is, i.e. without diode) for medium and low resolution. The timing markers give the delay between first falling edge of LOAD in a scanline and first change of the RGB line.

imp_shifter_med_res.png

imp_shifter_low_res.png


Note that because of the maximum sample rate of 100 MS/s of my logic analyzer the 16 MHz clock looks a bit uneven. In reality, it isn't. As mentioned earlier, DE has been excluded from the trace to have the full 100 MS/s (= 10 ns resolution) available.
Would be nice to know which conclusions you draw from these measurements.

PS: PM me if you want the full traces, to be opened with the Saleae software.
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Re: Different SHIFTER versions

Postby ijor » Wed Jul 11, 2018 7:18 pm

Thanks a lot!

Well, that's strange. Are you sure that the RGB signal traced starts right on the left border? Because it is quite late. If indeed that's the left border, then the logic must have been changed in comparison to the -38A version.

At low res the exact delay depends on the SHIFTER wakestate, but at med rez is fixed. Here it is one 16MHz cycle later than at the -38A. Of course, I have no way to be sure if the extra delay is at the initial phase of the processing or at the very end. At the end, after palette lookup, the delay is not relevant, it will just shift slightly the display. But considering that we are seeing some incompatibilities with the demos, it is almost sure that the extra delay is at an earlier stage.

I am hopefully getting an IMP SHIFTER myself to make more tests. It would be interesting to trace all the SHIFTER wakestates.
Still extremely busy for one or two ... decades ...

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Re: Different SHIFTER versions

Postby czietz » Wed Jul 11, 2018 7:36 pm

The traced RGB signal is one line of the (solid) background of the Desktop. I can confirm from my trace that it is indeed low for 640 pixels in medium res. So I'm quite sure that where you see it going low is indeed the left border.

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Re: Different SHIFTER versions

Postby tin » Wed Jul 11, 2018 8:03 pm

Here's a first baseline test with the 38A shifter in a non-IMP environment (100Mhz sampling, beginning of a solid green desktop line):
38a_la.png


Now that the Test Clip is set up, churning out more traces gets pretty easy and changing the shifter is a matter of seconds. Let me know if these traces are OK and I will produce the others in the next days.

Dang that the wiki is still broken (does that like have it's 10th anniversary soon?). Would be nice to gather the full traces there...
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Re: Different SHIFTER versions

Postby ijor » Wed Jul 11, 2018 8:34 pm

tin wrote:Here's a first baseline test with the 38A shifter in a non-IMP environment (100Mhz sampling, beginning of a solid green desktop line):
38a_la.png

Now that the Test Clip is set up, churning out more traces gets pretty easy and changing the shifter is a matter of seconds. Let me know if these traces are OK and I will produce the others in the next days.


Thanks again. Please include the 16MHz clock. The 32 MHz one is not very important, you can remove it. The phase of the 16MHz clock is more important.

Btw, note how the RGB signal here starts before the raising (trailing) edge of the 5th LOAD pulse, while at the traces provided by czietz taken with an IMP SHIFTER, it starts after it!

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Re: Different SHIFTER versions

Postby Smonson » Thu Jul 12, 2018 9:24 am

It also starts after the 5th LOAD in Troed's LE captures.

Image

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Re: Different SHIFTER versions

Postby ijor » Thu Jul 12, 2018 8:07 pm

Smonson wrote:It also starts after the 5th LOAD in Troed's LE captures.


But Troed's captures are at LOW rez, not at MED rez. Low rez always starts later than med rez, and the delay (at LOW rez) is variable and depends on the SHIFTER wakeup.

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Re: Different SHIFTER versions

Postby tin » Thu Jul 19, 2018 6:54 am

Just a quick status update. I don‘t have the traces yet (ah, the joys of getting sidetracked!) but I plan to bring the IMP board etc. to Nordlicht party and do traces there. There’s nothing like a quiet partyplace to do these things ;)
Monday there shall be traces.


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