| ??? 03/02/07 09:05 Read: times |
#134078 - As I said before ... HORSEFEATHERS! Responding to: ???'s previous message |
Erik Malund said: Yes, ... sometimes. It's clear that YOU don't care. It depends on how you define "works" though. I suppose it doesn't matter if your bus signs don't function 5% of the time, as nobody will notice. However, those reset chips don't help at all during the power-down transient. Kai's initial comment shows that the oscillator runs on until the Vcc is quite low.
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Richard Erlacher said:
I'm still wondering how to isolate the FLASH problem from the reset problem. I'm wondering how to control the circuit such that, when one's done with the investigation, one will KNOW whether the problem is in the power supply, the MCU, or the reset circuit. who gives a friggi'n hoot? When you use a supervisor and proper decoupling IT WORKS!, If you do not IT DOES NOT WORK (reliably). If the need is the flash, the tire pressure ot the kitchen sink is totally irrelevant.
ALSO, I have never seen the need for a supervisor related to switching power or not; however, when using switchers I have seen a somewhat stronger need for proper decopupling and filtering (which you, since you have switcher problems, evidently is incapable of implememting) Apparently it's been too much trouble for YOU, Erik, and others, to question the marketing literature. since you absolutely have to repeat this, I will too; I posted "thus you see the appnotes and datasheets with the stupid RC reset". How is that "not questioning the marketing literature" Erik
Get off the "it worked ages ago, why does it not work today". I'm simply pointing out that it's the on-board FLASH that's the problem on which you focus, rather than the RESET. The runaway MCU is an issue even if there isn't any FLASH. Do you want to pour leaded gasoline in your car because that was what you did ages ago?. With unleaded gasoline the engine design is a bit different, but, of course, that is HORRIBLE simply because your '54 Chevy ran on leaded gas.
Once again, you throw out a red-herring because you don't understand the issue. The two problems are NOT the same, and there's no relevance to your gasoline distraction. I don't care how many unverified and potentially faulty systems you've shipped. I might care about how many you've subjected to and had survive the appropriate 1000-hour (about 6 weeks) 100-piece temperature and voltage controlled testing. I imagine it's about ZERO. BTW, it's a '53 Chevy, and it still works fine with leaded gas. So, go ahead pour leaded gas in your new car, burn the engine and complain "why does it not work, it used to" I can't guess what you've been smoking ... <sigh> ... How many of these things have YOU tested, that is, operated in test mode, with, say, a half-dozen units under test at a time, all synchronized to a single clock and cycled, continuously over temperature and voltage conditions within specified limits for the standard 1000 hours? That's how you get reliability figures. I'll bet not ONE of the manufacturers has done that. Why? Because they all fail to discuss the failures and simply point to the RESET IC's and say, "those'll fix it." They've never even addressed the real problem, nor have you. I agree that the problem exists as much if not more during power-down than during power-up. The RESET IC can't help during power-down, though, since it is not specified what the MCU does while the power is dropping, nor is it specified what it does in response to RESET when power is dropping. That part is EASY to fix, though. One simply puts a transistor on the oscillator and stops it cold during a power-down. It is a synchronous state machine, after all. It might not even be a bad thing to pull Vcc to GND at the same time. As Lynn's said, the RESET is just an NMI. These MCU's aren't characterized for their operation during RESET in a power-down transient. I'd say it's anybody's guess whether they even recognize the RESET pulse at that time. RE |
