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Unconventional means for protecting 89C51

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techie

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89c51 lock bits

While trying to upgrade the firmware of instruments, I recently came across a lot of 89C51 processors from @tmel that could not be erased. When inserted in the Universal programmer, the Chip showed a No-connect error on one of the pins (probably a pin #29,30 or 31). The pin itself was physically OK. The processors were all working fine in thier original circuit. It looked that the original programmer had adopted some non-conventional means to protect the firmware of the chip from some expected lock-breaking efforts. Is this possible. Because I know the frgility of the 89C51's lock bits and would love to protect them in this more secure manner.
 

solvarg

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Re: Protecting 89C51

techie said:
While trying to upgrade the firmware of instruments, I recently came across a lot of 89C51 processors from @tmel that could not be erased. When inserted in the Universal programmer, the Chip showed a No-connect error on one of the pins (probably a pin #29,30 or 31). The pin itself was physically OK. The processors were all working fine in thier original circuit. It looked that the original programmer had adopted some non-conventional means to protect the firmware of the chip from some expected lock-breaking efforts. Is this possible. Because I know the frgility of the 89C51's lock bits and would love to protect them in this more secure manner.
What do you mean with "some non-conventional means to protect the firmware"?
Could you please describe it more in detail?

Regards
 

techie

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By "non-conventional" ways, I am pointing to the fact that a locked 89C51 can be erased since all the lock bits are also Flash based. As the 89C51 refused to get erased (programmer gives Error Erasing), I guess the person who programmed the 89C51 used some non-conventional way to lock the erasing of the IC. @tmel datasheet does not say anything of this sort.
 

mwpro

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Is there any unconventional ways to read a locked 89C51?
 

visioneer

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techie said:
By "non-conventional" ways, I am pointing to the fact that a locked 89C51 can be erased since all the lock bits are also Flash based. As the 89C51 refused to get erased (programmer gives Error Erasing), I guess the person who programmed the 89C51 used some non-conventional way to lock the erasing of the IC. @tmel datasheet does not say anything of this sort.
There have been an old trick to protect firmware code. Once upon a time, we've been burn the all the unused data pins with Vpp. I coulnd see a very short flash on the die through the window of the EPROM based micros. These trick might be adopted for now day FLASH micros.
 

mandrei

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Re: Protecting 89C51

There have been an old trick to protect firmware code. Once upon a time, we've been burn the all the unused data pins with Vpp. I coulnd see a very short flash on the die through the window of the EPROM based micros
That's amazing visioneer!!

The short flash on the die was in my opinion the wire bounding "burnning" (this is a tiny golden wire acting like a fuse).


You just give me an ideea haw to get rid of unused pins!!

1) charge an capacitor at some high voltage
2)dischage the capacitor thru unused pin


In this way the energy to break the wire bounding is controlable, not to damage the rest of the circuit (experimental we can determine the maximum Capacitance and Voltage)


PS:

Why getting rid of unused pins is inportant?

In some sensitive aplications unused wire bounding can act like an RF antena ( pertain RF waves to enter into the chip, worstenning the EMC performance)
 

hock

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Re: Protecting 89C51

gamegurus said:
Did you check this new verison?
h**p://chaokhun.kmitl.ac.th/~kswichit/89prog/index.html
I made this and it rocks #$#@!#$

my mail scanner has to say the following for ur file
please check
"Virus was found and deleted in http://www.sunrom.com/download/ProLoad2.zip:
Found virus PE_FINALDO.A in file ProLoad2.exe (in ProLoad2.zip)

The file is deleted."
hock
 

gamegurus

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Protecting 89C51

I wrote to the author and he says its false warning with Mcfee software from Trend Micro, Please update the latest signature and the false warning will go away,
This is due to the fact that EXE makes low level system calls
 

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