On 2010-09-23 10:37, Robin Abbott wrote: > I am surprised by the blowing of the chip on 12V applied to MCLR as all > inputs are protected by static protection diodes Traditionaly, this was *not* the case for the MCLR pin, right becuse it was the Vpp pin, of course ! You can not apply 12-13V Vpp if there would have been protection diods on MCLR. Don't know if they have added those diods on the MCLR pin in this case, have you verified that ? > which can usually handle > several mA which is below the current limit of most programmers. Do you k= now > if the J series is different on this pin ? The "difference" in that case would be that it *does* have the protections diods. > > Robin Abbott > Forest Electronics > > The home of WIZ-C ANSI C RAD development for the PIC ! > > www.fored.co.uk > 07801 718136 (+44-7801-718136) > > > -----Original Message----- > From: Oli Glaser [mailto:oli.glaser@talktalk.net] > Sent: 23 September 2010 02:43 > To: Microcontroller discussion list - Public. > Subject: Re: [PIC] A catalogue of cock-ups > > > > -------------------------------------------------- > From: "Philip Pemberton" > Sent: Thursday, September 23, 2010 2:10 AM > To: "Microcontroller discussion list - Public." > Subject: [PIC] A catalogue of cock-ups > >> Posted under PIC because this rather long rant relates directly to my >> frustrations with the J-series PICs. >> >> I've been prototyping some new hardware, based around a PIC18F85J50 >> and an FPGA. The FPGA handles the number crunching, the PIC is a >> general-purpose garden-variety USB to parallel bridge with some smarts >> (the FPGA allows it to share the ACQ RAM). >> >> The FPGA, however, is not the problem. The PIC is. >> >> >> 1) The pin-one marker on my parts is ambiguous. >> There are two round depressions in the chip face; one is a moulding >> mark, the other is the Pin 1 marker. How do you tell them apart? Hold >> the chip with the text horizontal and the Microchip logo at the top. >> Pin >> 1 is at the bottom left. Also, the moulding mark has a bit of text >> inside it, though you need a strong magnifier and a bit of chalk (or a >> paint marker and some IPA) to see it. >> >> This cost me one chip. =A34 down the pan. Thanks, Microchip. >> >> >> 2) The MCLR pin can't handle 12V. >> MCLR on these chips is specced to run at about 5V *absolute maximum*. >> The real limit is Vdd (usually 3.3V). If you change the device type >> during an MPLAB run, MPLAB may not save that device type if it crashes..= .. >> >> I just had an MPLAB crash. Restarted, and selected the PICKit2. MPLAB >> had reselected the PIC18F252 I was using before. BANG goes another chip. >> =A38 down the pan. >> >> I think I'm going to solder a 4.1V Zener diode across the MCLR test >> pad and a conveniently located ground via... >> >> Tomorrow I get to fire up the SMD workstation and replace this chip. >> Which is going to be great fun since it's surrounded by 0603 >> decoupling capacitors and my vacuum pick-up pen is shot. Blu-tak on a >> cocktail stick, anyone? >> >> And I haven't even gotten to a point where I could upload the LED >> blinker or FPGA boot test code yet. >> >> AARGH. Sometimes it's just not worth chewing through the leather >> straps in the morning... I'm going to bed. > > lol, I know how you feel... > > Doing a similar kind of thing with a PIC18F24J50 and an FPGA at the momen= t > too - has had it's share of mishaps also (though it's working very well n= ow) > but that's all part of the fun... :-) It does bug me that some > manufacturers don't make pin 1 less ambiguous - doesn't seem that difficu= lt > to do yet everyone does it differently - bevelled edges, dots, depression= s, > bars, text etc etc... > I quite like the J series though from first experience with stuff like th= e > remappable peripherals, although I'm using an ICD3 which I prefer to my > PicKit2 nowadays - seems very reliable, programs real quick and debugs we= ll. > > Also on the 18F24J50 pin 1 is marked well with a single round depression. > > > -- > http://www.piclist.com PIC/SX FAQ& list archive View/change your members= hip > options at http://mailman.mit.edu/mailman/listinfo/piclist > > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .