| ??? 10/03/07 22:54 Read: times |
#145361 - Well maybe it's not a red herring after all Responding to: ???'s previous message |
Erik Malund said:
Richard Erlacher said:
Not exactly. I did indicate that if the rise time of Vcc was slow, the PSU was inadequate. What is a PSU? Power Supply Unit ... see often-wrong, but not this time, Wikipedia I'd be interested in how you do that with a signal that's active-high and pulled down, yet driven with a totem pole.
answered, at least, twice in this thread. You may think so, but you haven't. If you disagree, please point to the precise statement you made, and where you made it. 2) who on eatrh would, these days. use a TTL supervisor?
Who knows? I doubt there were such things when TTL was the prevailing technology. so all thjat stuff about TTL levels was another red herring to get uys away from seeing hiw ridiculously feeble you arguments agains supervisrs are? It was not a red herring, but, rather an explanation of why, in 1979, I decided against using 805x's unless it couldn't be avoided. If Vcc is out of spec, what is the MCU going to do with a RESET that's not at a valid Vcc level? How will it interpret the signals from other internal resources, flash, etc?
from a datasheet: min max VIH1 Input high voltage, XTAL1, RST 0.7VCC VCC+0.5 V so, whatever Vcc is if reset is above 0.7Vcc the chip is reset. from the DS89C430..450 datasheet, http://datasheets.maxim-ic.com/en/ds/DS8...89C450.pdf page 2: Reset Trip Point (Min Operating Voltage) (Notes 2, 3, 4) min typ max VRST 3.95 4.125 4.35 V what does a uCs reset output have to do in a supervisor discussion? another red herring to get uys away from seeing hiw ridiculously feeble you arguments agains supervisrs are? I'm afraid you're off-base here. The RESET output spec is farther down the page. Why would I do that? then WHY THE HECK do you keep 'suggesting' thet othere try this, verify that, make a test rig for those .... Erik I'm not suggesting anything! I've already observed that RESET from a supervisor is sometimes irrelevant during decaying Vcc. Engineers have rigorous procedures they follow when designing and developing a product. They develop a set of requirements. They develop a set of specifications that meet those requirements. They develop a set of test procedures that will prove that they've met those specifications. They implement what is set forth in those specifications. They then apply procedures set forth in the test specifications. How long, and over what mechanical and environmental stresses their product is tested can vary considerably, but some rigorous testing must precede shipment of the first batch of product. If you don't thoroughly and rigorously test your hardware, you are not doing your job. Part of your job as a design engineer is to design to a specification. Your job as a designer is to meet that specification at the lowest possible cost, and to ensure that every requirement set forth in the specification is met, and no money is squandered doing things not required in that specification. Only rigorous post-assembly testing can ensure that all requirements are met under all specified conditions. BTW, Erik, maybe you need to get a "typing tutor" program, or at least read your posts before sending. Some people may have trouble figuring out what you mean. RE |
