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Richard Erlacher
12/06/12 09:43
  12/06/12 09:47

Read: 1014 times
Denver, Co

#188972 - Where this began ... at least for me ...
Responding to: Kai Klaas's previous message
Several years ago, I was playing with 8051 in a physically small on-off that was acting strangely. In the course of my investigation, I noted that the external BBRAM I was using with it was frequently corrupted. This was not an ISP-capable or even FLASH-based part. It was an AMD 8751 of 1980 or thereabouts vintage. What I had done was to wire up a circuit based on an application example, including the "classic" RC reset circuit with the 10 uF cap and 8K2 pulldown resistor. With the exception of the program store corruption, everything seemed to work properly. Consequently, I was poking around in the circuit to see whether I could find any cause.

At one point, having read the tales about flash corruption, I added that old DS1232 supervisor to the circuit, hoping that the problem would "go away" as it often had done for others. However, that was not what it did.

Now, this was a very small board, wire-wrapped with very little space for any other components, and some of the decoupling cap's were pretty sizeable eletrolytics, because I had them on the table when I built the circuit. I suspected something was peculiar in connection with the RESET during power-down. Only then did I discover that external memory was being accessed despite the presence of active RESET. That was not an ISP-capable MCU, nor was it flash-based. I had, of course, the opportunity to examine the BBRAM content in a programmer, which is how I reprogrammed the part. That's how I knew the BBRAM was, in fact, being corrupted. If it had been a FLASH-based part, I probably never would have noticed that this was happening, since I can't put 'scope probes on the internals of the MCU.

I did, however, put probes on RESET, nRD, nWR, and nPS. Once I saw activity on the three external memory controls during RESET. I substituted several other 805x's, as this was actually an 8031 circuit, since I'd not programmed the internal EPROM. The behavior with respect to the BBRAM was consistent throughout, though I did not verify that the content of the BBRAM was always modified in the same way. When I removed the 330 uF electrolytic from the Vdd rail, the problem "went away" ... almost ... and when I set the circuit up on a test fixture that repeated the set of stimuli needed to cycle power and RESET, I found that the occurrence of this post-RESET run-on occurred seldom once the swamping capacitor on Vdd was removed, but not entirely. At the time, I did not monitor Vdd during the repetitive experiment, though I did monitor those three external memory control signals during RESET. Whenever this event occurred, the system took note. Since it was already set up for 1000-hour testing, that's how long I ran it with the swamping cap removed. I don't remember how many times it occurred, though I suppose it's on a printout somewhere. It was much less frequent than with the swamping cap in place, as it occurred nearly every dozen-or-thereabouts repetitions, with that cap in place, which was based simply on the fact I had to reload the BBRAM about that often. I really don't know what I should conclude from this, as it was not a rigorous examination.

BTW, I don't dislike the ATMEL parts, as I've not used them. I do, however, dislike the ATMEL corporate culture, as demonstrated in that incident I have repeatedly described, and which I won't repeat here. That incident persuaded me that, so long as there were other manufacturers who produce suitable components, I don't have to subject myself of my clients to the ATMEL abuses. It's just a personal choice, but it did cost a lot of time and money, resulting, probably, in a lost opportunity in the market. This was caused by their culture of consistently denying their faults and lying about what was going on in their development, assuring us that things were just fine, when it was quite apparent that they were not.

If you use ATMEL products, by your own choice or someone else's, I bear you no ill will. I just won't use their products myself, nor will I ever recommend them to anyone else, unless I see a major change in their corporate culture. I admit that my experience was restricted to one with a French design team, and this sort of behavior is an established and centuries old culture in France, but it did not make me a trusting and loyal ATMEL customer.

The fact that I don't use their products doesn't prevent me from reading their datasheets and white-papers, though it does leave me somewhat suspicious of what they say.


List of 33 messages in thread
C8051F231 experiences      Daniel Contarino      11/30/12 14:43      
   another solution      Erik Malund      11/30/12 15:11      
   The probabilities are low...      Daniel Contarino      11/30/12 18:34      
      think about what happens when you add a finger      Richard Erlacher      11/30/12 22:55      
         The point is ...      Daniel Contarino      12/01/12 03:08      
            Yes ... the underlying issue is the flash ...       Richard Erlacher      12/01/12 11:28      
               Out of my office, but...      Daniel Contarino      12/01/12 14:05      
                  Don't think in Vcc, ESD or hum...      Daniel Contarino      12/02/12 09:24      
   Apparently several C8051F2xx parts have the same pinout      Richard Erlacher      12/01/12 14:25      
   Characteristic for in system programmable flash micros...      Kai Klaas      12/01/12 18:25      
      All too true ... sadly ...       Richard Erlacher      12/01/12 20:13      
         Power-on slope rate...      Kai Klaas      12/02/12 05:31      
            Sorry, my post should be here, no up there...      Daniel Contarino      12/02/12 09:58      
            Have you any basis for that rate?      Richard Erlacher      12/02/12 10:15      
               Vdd ramp time      Maarten Brock      12/03/12 06:15      
               Some datasheets show numbers...      Kai Klaas      12/03/12 07:05      
                  Those aren't the "usual" 805x-core MCU's      Richard Erlacher      12/03/12 17:43      
                     There aren't many "usual" 8051-cores anymore...      Kai Klaas      12/03/12 18:13      
                        How dangerous power ups can be...      Kai Klaas      12/04/12 06:20      
                           I believe it      Richard Erlacher      12/04/12 08:59      
                              (dV/dt) examples      Jim Granville      12/04/12 13:14      
                                 They don't know it either...      Kai Klaas      12/04/12 18:49      
                                    dV/dT etc       Jim Granville      12/04/12 21:39      
                                       reset request...      Kai Klaas      12/05/12 06:21      
                                          That's what disturbs me greatly      Richard Erlacher      12/06/12 00:19      
                                             It IS disturbing!      Kai Klaas      12/06/12 08:02      
                                                Where this began ... at least for me ...       Richard Erlacher      12/06/12 09:43      
                                                   So, you took the hard road...      Kai Klaas      12/06/12 10:41      
                                                      We've all had that experience       Richard Erlacher      12/06/12 16:23      
   probable cause      Brent Wilson      02/04/13 20:32      
      Brent, this is very nice      Erik Malund      02/05/13 06:38      
         forum no longer down      Maarten Brock      02/05/13 07:33      
      Thank you!      Daniel Contarino      02/05/13 15:04      

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