As far as the atmel (avr): Almost all my projects use AVR microcontrollers, Due to the R&D nature of my work I've /always/ pushed the envelope. I use data sheets as a guideline and nothing else. Years ago I poked around publically at the avr forum about the idea of exploiting undocumented instructions. People in general were not interested in anything out documentation parlance. *Burn in * is second nature to me. Both profiling and application.
As far as powering down a MCU while keeping a clock running, The easiest solutions i've found are to use a field effect, i prefer jfet but signal fets would work just as well. This way you don't need to be concerned about back feeding power from IO or in this case the clock/oscillator input. Steve On Fri, Nov 25, 2011 at 4:21 PM, Robert Atkinson <robert8...@yahoo.co.uk>wrote: > > > Hi, > > Microchip cerainly condone using input protection diodes of PIC devices as > clamps. There are application notes for zero-crossing detection which > connect the input to the 115V AC line via a resistor. Note that these are > intentional protection diodes, not unavoidable parasitic junctions. Typical > Absolute max clamp current (inc. 16F628) is +-20mA. As a side note, when > using these diodes for ESD protection, Microchip recommend using 0.01uF > supply decoupling capacitors close to the chip rather than 0.1uF. This > reduces the peak current. Trace inductance limits the effect of more > distant capacitive loading. > > Robert G8RPI. > > > ________________________________ > From: Attila Kinali <att...@kinali.ch> > To: Discussion of precise time and frequency measurement < > time-nuts@febo.com> > Sent: Friday, 25 November 2011, 8:17 > Subject: Re: [time-nuts] Clocking a PIC16F628A from a Rubidium Standard > > On Thu, 24 Nov 2011 12:05:13 -0700 > Kevin Rosenberg <ke...@rosenberg.net> wrote: > > > Since frequency reference sine wave can exceed Vdd, you want to current > > limit the external clock. For example, an unterminated TBolt puts out > 0-7V > > Pk-Pk. Atmel, in an app note where they hook up the pins of an AVR > > to 220V mains, states the over/under voltage protection diodes should > > not carry more than 1 milliamp of current. But, you should both read > > the datasheet for the output voltage of the Efratom and measure Pk-Pk > > voltage output at the point of your PIC. > > Using the protection diodes as part of the circuit is bad design practice. > Use instead explicit shottky diodes (like BAT54S) for clamping. > Better would be to use a resisitive divider (probably with a capacitive > divider in parallel), a coupling capacitor to connect it to the clock > input. You can limit the swing of the signal to less than 1V as the clock > input doesnt require a big signal (when using a crystal, the "signal" can > be as low as a few mV, depending on the chip) > > > Attila Kinali > > -- > Why does it take years to find the answers to > the questions one should have asked long ago? > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.