Author Topic: Erasing Microchip ATF series CPLD after setting security fuse - possible?  (Read 574 times)

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Offline deanclaxton

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I'd like to know if there is a way to erase an ATF1500 series CPLD after setting the security fuse.

Is there a method similar to the 12V OE1 trick used to re-enable ISP if JTAG pins are used for IO? This doesn't appear work if the security fuse is set.
 
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Offline deanclaxton

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Re: Erasing Microchip ATF series CPLD after setting security fuse - possible?
« Reply #1 on: September 05, 2020, 08:54:24 am »
Some more info on these chips here : https://www.eevblog.com/forum/fpga/atmel-atf150x-cpld-and-wincupl/

I just need to find out whether it's possible to recover a chip with the security fuse set without removing the chip from the board and using some $$$$ programmer.
 

Offline mikeselectricstuff

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Re: Erasing Microchip ATF series CPLD after setting security fuse - possible?
« Reply #2 on: September 05, 2020, 09:22:03 am »
I've never come across any reprogrammable chip that can't be erased after securing.
I'd think there would be a warning in the datasheet if it was not possible, though if there are multiple programming methods there may be some limitations.
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Offline deanclaxton

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Re: Erasing Microchip ATF series CPLD after setting security fuse - possible?
« Reply #3 on: September 05, 2020, 11:19:46 am »
yeah - I'd like to be able to erase and re-program the device after securing it. I'm sure there would be a method - just can't find any info out there on how to do it :)
 

Offline mikeselectricstuff

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Re: Erasing Microchip ATF series CPLD after setting security fuse - possible?
« Reply #4 on: September 05, 2020, 02:04:23 pm »

I seem to remember the /JW PIC parts were unpleasant in that respect, you could erase the code/data area of the chip with UV but not the security bits as they were masked, rendering the chip nicely blank but utterly useless as anything other than a reminder to not do it again.
From my memory, they just had a different threshold on the security bits so they took longer to erase than the code memory
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Offline NorthGuy

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Re: Erasing Microchip ATF series CPLD after setting security fuse - possible?
« Reply #5 on: September 05, 2020, 04:11:20 pm »
I've never come across any reprogrammable chip that can't be erased after securing.
I'd think there would be a warning in the datasheet if it was not possible, though if there are multiple programming methods there may be some limitations.

Newest Microchip PIC24s have security setting which prevents external erase/re-programming completely. So, this is certainly possible.
 

Offline up8051

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Re: Erasing Microchip ATF series CPLD after setting security fuse - possible?
« Reply #6 on: September 05, 2020, 06:29:25 pm »
My parallel programmer Labtool48 support this chip and has option Erase, but I haven't any ATF15xx  to test erase after secure.
 

Offline deanclaxton

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Re: Erasing Microchip ATF series CPLD after setting security fuse - possible?
« Reply #7 on: September 06, 2020, 08:08:03 am »
My parallel programmer Labtool48 support this chip and has option Erase, but I haven't any ATF15xx  to test erase after secure.

Is there any way to view the programming algorithms? It would be very interesting to see which pins its using, and what voltages are applied (assuming the erase actually erases a chip with security fuse set).
 

Offline TomS_

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Re: Erasing Microchip ATF series CPLD after setting security fuse - possible?
« Reply #8 on: September 21, 2020, 11:31:03 am »
I suppose you could hook up an oscilloscope to a bunch of pins, capture the waveforms, and reverse engineer it from there.

I believe that is part of the process people on this forum used to reverse engineer the programming algorithm for the Padauk microcontrollers and build a programmer for them.

Ive got a scope, but would just need access to a programmer.  ^-^
 

Offline David Hess

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Re: Erasing Microchip ATF series CPLD after setting security fuse - possible?
« Reply #9 on: September 22, 2020, 07:36:59 pm »
If these are EPROM based, then they can be erased using x-rays instead of ultraviolet to get past the packaging and security.
 


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