topic Re: OTP changed spontaneously. in LPC Microcontrollers

OTP changed spontaneously.

lpcware — Wed, 15 Jun 2016 18:18:58 GMT

Content originally posted in LPCWare by Ivar on Fri Aug 21 17:30:50 MST 2015
Hi,

I use the OTP bank 3 word 1 as the device serial number.

From a total of 5000 devices sold about 1% changes without being reprogrammed.

When this happens, 0xFFFFFFFF is recorded in this place and I use the bank3 word 2 as serial number. Similarly, it also I use the third word.

Amazingly, a word with 0xFFFFFFFF is sometimes handles certain bits off! Sometimes the word was not used and is read with a few bits on.

Here are some examples of when the word should be zero (Hex):
00000010, 00000010, 00000010, 00000010, 00000040, 00000100, 00000810, 00001100, 00002000, 00008000, 00008040, 00200000, 00400000, 00400100, 00408000, 00600000, 01000000, 04000000, 04000040, A0000000, 81000010, 80400000, 80000000, 80000000, 80000000, 80000000, 10000000, 20000000, 21000010, 24000000

And these examples should be FFFFFFFF (Hex):

FFFFFFEF, F8FFFFFF, EFFFFFFF, FFFFFFFE.

Very important: only one program write the OTP and runs during device production. After just run a program that reads the OTP.

Investigating a specific device with this problem, it has been observed that when the appliance is initially on the OTP was ok. Waiting for about 2 minutes to warm up the processor (about 40 ° C) the problem appears repeatedly. After a few minutes off, the device cools and the OTP back to normal.

But most devices with problem permanently alter the OTP, regardless of whether cold or hot.

I also use the OTP to change the boot and I had no problem with that.

How can I solve this problem?

Thanks.

Ivar.

Re: OTP changed spontaneously.

lpcware — Wed, 15 Jun 2016 18:19:00 GMT

Content originally posted in LPCWare by mysepp on Tue Nov 03 12:04:24 MST 2015
Have you seen latest errata about OTP?

Re: OTP changed spontaneously.

lpcware — Wed, 15 Jun 2016 18:19:00 GMT

Content originally posted in LPCWare by Ivar on Tue Nov 03 15:43:38 MST 2015
Thanks for the answer.

I had not seen yet.

Now I read the errata 6.5 04-Sep-2015 and seems to be the case with us. Our problem is also associated with temperature, as described.

Unfortunately we do not have to change the hardware as suggested. Our product has been manufactured.

Do you have any suggestions on how to solve only by software or at least minimize the problem?

Thanks.

Ivar.

Re: OTP changed spontaneously.

lpcware — Wed, 15 Jun 2016 18:19:01 GMT

Content originally posted in LPCWare by mysepp on Tue Nov 03 23:07:48 MST 2015
Perhaps something with built-in EEPROM, additional checksum, both? Fallback to EEPROM when there is an error?
Or put part of the OTP content in flash?

Re: OTP changed spontaneously.

lpcware — Wed, 15 Jun 2016 18:19:01 GMT

Content originally posted in LPCWare by Ivar on Wed Nov 04 15:26:34 MST 2015

Your suggestions are great. Thank you for them.

OTP Bank 0 has recorded the A "UNIQUE ID". You can not rewrite it.

Similarly to Banks 1-3, does the "UNIQUE ID" can also accidentally change? The ERRATA 6.5 is not clear about it.

Thank you very much.

Ivar