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Contributor
Contributor
8,215 Views
Registered: ‎08-07-2008

Erasing an EEPROM

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When Impact erases an EEPROM (an XCF32, for example), does it just set things back to all 1, or can it be made to write a random pattern first?

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Xilinx Employee
Xilinx Employee
9,450 Views
Registered: ‎08-13-2007

Re: Erasing an EEPROM

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If you need a specific pattern for a specific usage (e.g. sanitization), you could alway do this manually, e.g.

 

Open iMPACT, open a boundary scan window, and initialize the chain with the cable connected and board powered on
erase the PROM

perform a Readback operation on the PROM, specify a target MCS file
convert the read mcs to .hex: promgen -r <filename>.mcs -p hex -o <filename>.hex
modify this hex file with the desired data/pattern with a text editor, making sure to keep the same number of characters
convert the new hex back to mcs: promgen -r <filename>.hex -p mcs -o <filename>.mcs

use iMPACT to program the new .mcs

 

Of course, don't expect th FPGA to successfully configure this way. Might be a good idea change the FPGA's MODE M[2:0]  pins to something like JTAG or a slave mode instead of a master mode. to avoid  actually trying to configure with this pattern later...

 

Cheers,

bt

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5 Replies
Instructor
Instructor
8,213 Views
Registered: ‎08-14-2007

Re: Erasing an EEPROM

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The XCF series are Flash, which is electrically erasable, but not "EEPROM" in the usual sense of

byte re-writable devices.  It gets erased to all 1's because there is no other "erased" state of the

flash.  You can request that Impact fill unused locations with a value other than FF (all ones), but

it can't do that during the erase, because any other value would not leave the flash writable.

 

-- Gabor

-- Gabor
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Xilinx Employee
Xilinx Employee
9,451 Views
Registered: ‎08-13-2007

Re: Erasing an EEPROM

Jump to solution

If you need a specific pattern for a specific usage (e.g. sanitization), you could alway do this manually, e.g.

 

Open iMPACT, open a boundary scan window, and initialize the chain with the cable connected and board powered on
erase the PROM

perform a Readback operation on the PROM, specify a target MCS file
convert the read mcs to .hex: promgen -r <filename>.mcs -p hex -o <filename>.hex
modify this hex file with the desired data/pattern with a text editor, making sure to keep the same number of characters
convert the new hex back to mcs: promgen -r <filename>.hex -p mcs -o <filename>.mcs

use iMPACT to program the new .mcs

 

Of course, don't expect th FPGA to successfully configure this way. Might be a good idea change the FPGA's MODE M[2:0]  pins to something like JTAG or a slave mode instead of a master mode. to avoid  actually trying to configure with this pattern later...

 

Cheers,

bt

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Contributor
Contributor
8,201 Views
Registered: ‎08-07-2008

Re: Erasing an EEPROM

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More steps than I'd hoped for, but I can build a sanitization procedure from this. Thanks!

 

Yeah, I use "EEPROM" purely out of bad habit. I still remember using UV erasers and putting stickers over the little windows. I'm old. :(

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Teacher rcingham
Teacher
8,086 Views
Registered: ‎09-09-2010

Re: Erasing an EEPROM

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> I still remember using UV erasers and putting stickers over the little windows. I'm old. :(

I remember putting a windowed EPROM in the programmer backwards and having it light up!

------------------------------------------
"If it don't work in simulation, it won't work on the board."
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Instructor
Instructor
8,084 Views
Registered: ‎08-14-2007

Re: Erasing an EEPROM

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@rcingham wrote:
> I still remember using UV erasers and putting stickers over the little windows. I'm old. :(

I remember putting a windowed EPROM in the programmer backwards and having it light up!

Back in 1979 I remember that we were just starting to build products with microprocessors

instead of just TTL.  We had a new programming guy (it wasn't really "software" in those days)

who had the same experience.  He found it so amusing that he pulled out another EPROM

and showed me.  At the time the 2716 EPROM cost us about $35.  As an aside, the EPROM

and the programmer were both made by Intel.  Apparently adding circuitry to sense incorrect

insertion would be bad for their bottom line...

 

-- Gabor

-- Gabor
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