Hysteresis on dsPIC ports?
in [Design]
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From: Joerg on 26 Jan 2010 11:59 Robert Baer wrote: > Joerg wrote: >> Hello, >> >> This really blows my mind and I think I've arrived at the decision not >> to use their uC in the future. But a client does. It's a dsPIC and >> while the datasheet says that the IO ports have Schmitt >> characteristics there is no mention of how much hysteresis. So, I >> dutifully opened a support ticket asking for the hysteresis. The >> answer came promptly but floored me. They do not know (!). Sounds like >> a textbook answer from Outsourcia. I shall contact the sales office >> and if our app is deemed "worthy" they might or might not process such >> request. >> >> <shaking head> >> >> Anyhow, does anyone know what the hysteresis on dsPIC ports is? >> > Measure it! > Then publish and take *all* of the credit. I don't have one here and the client hasn't built it yet. Plus we'd need guaranteed limits, not just from one wafer. MicroChip called it "unpublished electrical characteristics". Pathetic. Taught me a lesson about these products. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joel Koltner on 26 Jan 2010 12:16 "Joerg" <invalid(a)invalid.invalid> wrote in message news:7s8l6fFe36U3(a)mid.individual.net... > Oh yeah, he'd tear them apart in mid-air :-) My suspicion is that PICs are so popular these days that their "support" department is the same as you get with most software companies -- the 1st tier are essentially just there to read the data sheet back to you, since the answers to a very large percentage of support requests are found right there. Of course, they should have automatically escalated your request to the next tier when it became clear they didn't know the answer to your specific question. Someone's making a judgement call that that spec isn't very important, I'd guess, which is poor. ---Joel
From: Jan Panteltje on 26 Jan 2010 12:41 On a sunny day (Tue, 26 Jan 2010 08:59:56 -0800) it happened Joerg <invalid(a)invalid.invalid> wrote in <7s8lcgFe36U4(a)mid.individual.net>: >I don't have one here and the client hasn't built it yet. Plus we'd need >guaranteed limits, not just from one wafer. MicroChip called it >"unpublished electrical characteristics". Pathetic. Taught me a lesson >about these products. Bull, there is a large difference between 'Schmitt characteristics' and 'is a Schmitt trigger input'. It means in fact that you *cannot* use it as a Schmitt trigger input, but that you *should expect* a Schmitt trigger like behaviour when driving it with some ramp. I am not saying Microchip is all in the clear here, but *unless* it is specified as a Schmitt trigger input, you cannot assume so. It is simply nice that they bothered to point out that gate's behaviour, they did not have to. LOL
From: Joerg on 26 Jan 2010 12:49 Joel Koltner wrote: > "Joerg" <invalid(a)invalid.invalid> wrote in message > news:7s8l6fFe36U3(a)mid.individual.net... >> Oh yeah, he'd tear them apart in mid-air :-) > > My suspicion is that PICs are so popular these days that their "support" > department is the same as you get with most software companies -- the > 1st tier are essentially just there to read the data sheet back to you, > since the answers to a very large percentage of support requests are > found right there. > Blowing off a client with a remark along the lines of "the sales guys will dig into that if your sales volume is deemed worthy" is, ahem, not a very polite way to deal with their most important part of biz, the sales channel. > Of course, they should have automatically escalated your request to the > next tier when it became clear they didn't know the answer to your > specific question. Someone's making a judgement call that that spec > isn't very important, I'd guess, which is poor. > Yep. So far I haven't used PICs in any of my "from scratch" designs. And I guess after this episode I won't. I need parts that are characterized a bit more thorough than those. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 26 Jan 2010 13:05
Jan Panteltje wrote: > On a sunny day (Tue, 26 Jan 2010 08:59:56 -0800) it happened Joerg > <invalid(a)invalid.invalid> wrote in <7s8lcgFe36U4(a)mid.individual.net>: > >> I don't have one here and the client hasn't built it yet. Plus we'd need >> guaranteed limits, not just from one wafer. MicroChip called it >> "unpublished electrical characteristics". Pathetic. Taught me a lesson >> about these products. > > Bull, there is a large difference between 'Schmitt characteristics' > and 'is a Schmitt trigger input'. > It means in fact that you *cannot* use it as a Schmitt trigger input, > but that you *should expect* a Schmitt trigger like behaviour when driving it with some ramp. > I am not saying Microchip is all in the clear here, but *unless* it is specified > as a Schmitt trigger input, you cannot assume so. Nope. Quote from the dsPIC datasheet: "All I/O input ports feature Schmitt Trigger inputs ..." > It is simply nice that they bothered to point out that gate's behaviour, they did > not have to. > LOL > Sorry, for my line of work that is not good enough. How come Texas Instruments is able to diligently specify the guaranteed min-max values? See page 24: http://focus.ti.com/lit/ds/symlink/msp430f2011.pdf _That's_ how a good datasheet is written. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |