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Richard Erlacher
06/20/12 09:13
Read: 649 times
Denver, Co

#187806 - I have to agree with Hal, it can't be done ...
Responding to: Hal Albach's previous message
I've been requesting a schematic, but you've withheld it. Surely there's a way to present it in readable form.

The fact is, there's no way on earth, or any where else, for that matter that you can program this particular MCU, if the datasheet link you've provided refers to the actual device you're using.

No bootloader I've ever encountered will program this part, as it has no programmable program memory. It is either mask programmed at the factory, or it is a <one-time-programmable (OTP) to which the datasheet also refers.

Your original post post says

I was trying to repair a circuit that contains the SUB-C501 microcontroller with external EPROM, SRAM and some gates. In order to repair it, i wrote a simple program in assembly and i send in Hyper Terminal a string. The program works fine in working circuis. But in circuits which have problem i do not take anything in Hyper Terminal and checking the circuit i measure something strange. I measure with oscillator the ports of high byte adress in Port2 and i see that all take some time level high, something that do not hapen in working circuits.

Does anyone cope with such a problem, does anyone can me explain what can be going wrong?

The circuit that i send is not real because the real one I do not have it because everything I take it in paper or on pc monitor. Is not that I do not want to show the circuit.

I'm curious what you mean by "Repair". Has this circuit ever done what you want?

You refer, later to using a '573 latch, implying that you've got an external address/data bus, yet you don't refer to the external memory for which that address/data bus is created.

The only realistic approach to using this chip that occurs to me is to have TWO separate external program memory devices, one of which resides at address 0x0000, and the other at, say, 0x2000. The one at 0x0000 would contain a bootloader, which you never modify, and the other would be a FLASH or FRAM, or BBRAM, which can be programmed under the control of your bootloader. The process of loading the bootloader would not be straightforward, as you have to have an external programmer of some sort in which to do that.

Please answer the following questions ...

(1) Has this circuit ever functioned properly?
(2) What did the circuit do?
(3) If it once functioned properly, what has happened to it in order to cause it to stop?
(4) What sort of external memory component(s) are you using?
(5) How is the /EA pin on your MCU connected?

That may help.

By now, I'm sure you have concluded that it might have been useful to read the datasheet for this particular MCU before attempting to use it. I submit that that will always be the case.


List of 14 messages in thread
circuit repair, high level of all adress bytes      John Papas      06/15/12 15:16      
   what's on P2 is not that intersting initially, ...      Erik Malund      06/15/12 16:46      
      oszi daten      John Papas      06/18/12 12:16      
         depends on the app, but still      Erik Malund      06/18/12 12:51      
      we'll need a schematic, I believe.      Richard Erlacher      06/18/12 19:38      
   general guidelines      Mahmood Elnasser      06/18/12 22:45      
   RE      John Papas      06/19/12 03:39      
      Hardware check      Mahmood Elnasser      06/19/12 07:34      
      anyhow this begs a question      Erik Malund      06/19/12 09:24      
         Replay      John Papas      06/19/12 15:52      
            It wouldn't hurt to know how you've connected your hardware      Richard Erlacher      06/19/12 17:03      
               new      John Papas      06/20/12 07:12      
                  Just curious...      Hal Albach      06/20/12 07:34      
                     I have to agree with Hal, it can't be done ...      Richard Erlacher      06/20/12 09:13      

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