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Noise pulses on Position Compare on a Clipper
#1
I'm using a Turbo PMAC 2 Clipper to operate machines with 3-5 axes. I use the position compare hardware pulses to fire a droplet dispenser or laser during motion. We have almost 20 years practice in our company doing this.

I now have for the first time, and only with one Clipper card, seen random noise pulses on an OR of all four EQU lines of the Clipper. They show up whenever they want to, no motion needed. The card has gone back for service, so I don't have any at hand.

However, having sorted out all kinds of external causes, I just (re)discovered that on this card, I had set the Position Compare Channel Select I7011 to 1, because the manuals (both PMAC and Turbo PMAC) say it cannot be anything else:

"I7m11 performs no effective function, so is always 1. It cannot be set to 0."

(I7021, I7031, I7041 and I7111 are all 0.) All other cards we have used have happily lived with 0 for that variable. Because this machine is more complex than all others that we have built, I wanted to make sure that I go strictly by the book. Did I get fooled by a documentation error?

Hans-Jochen Trost
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#2
This was the case for the original “servo gate” but not with the later “FPGA” versions.

I have the “later” FPGA version and have verified it can be set and saved to “1”, but note that it will have no effect.

The documentation is correct for the original “servo gate” version. I will bring this to the attention of the ODT development group.
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#3
Note that it is possible you may have an “older” FPGA code that did have an issue with noise on that input.

This was “fixed” on later versions of the FPGA. My testing was done on an earlier version of the FPGA code. An RMA will “update” the FPGA code.
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#4
Steve,

thanks for the feedback. A replacement card is due in any day. I will test it on an in-house development system (3 stepper motors, laser) and on the real machine (5 servos in a gantry system with 2 of the in the y axis, laser) and let you know what comes out of it.

Jochen
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