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PIC24FJ64GA004 code memory problem

 
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fuxafak



Joined: 08 Nov 2013
Posts: 11
Location: Istanbul

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PIC24FJ64GA004 code memory problem
PostPosted: Tue Dec 23, 2014 10:54 am     Reply with quote
Hi All,
I use PIC24FJ64GA004 for an automation project. The board includes uC, Nordic nRF905 tranceiver, Micron m25pe20 serial flash memory and offline buck converter. Board has relatively high EMI because of power supply circuit. I have very strange problem which is:

We have totally 250 circuit which are working together. My code has a bootloader code at starts and then application code below. If new firmware are sent from router, device would write it to ext memory and then when it restart itself it reads all memory from external memory and write them to code memory (from beginning to end as normal). But i have newer use that function for that devices yet. Despite this, some devices code memory last byte or last page is change to 00. If somehow my code erase the code memory, it will be all ff.

Code:

:104D4000FFFFFF00FFFFFF00FFFFFF0000FEFF006F
:104D50000000000000000000000000000000000053


It is like that. All these memory should be ff as my compiled code. So, i dont know how these bytes turned into zero :(

My opinions:
EMI can cause fault data at spi pin with external memory or icsp pin. It causes faulty things and the code memory are gone Smile But external memory should sent some data like
Code:

:104D50000000000000000000000000000000000053

to erase that memory. These code hasn't any code because i didn't upgrade firmware yet. So ext memory also should have all ff for code memory. And another darkness about these opinion is: If external memory fails at the beginning of code, the remaining code memory should also corrupted. But it all verified.

Somehow, uC code memory bulk pin goes to ground for spesific addresses (probably only last page) and it makes these bytes all zero! I don't know where the code memory bulk pin is or whether is it being Smile

Hmm, please give your opinions about that. That's so weird..

Thanks
ufuk safak
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-ufuk safak-
Istanbul Technical University
temtronic



Joined: 01 Jul 2010
Posts: 9226
Location: Greensville,Ontario

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PostPosted: Tue Dec 23, 2014 12:34 pm     Reply with quote
You MUST get rid of the EMI !
sounds simple BUT can be a nightmare to do. You need to add filter caps, use wider traces, proper grounds, redesign PCB layout, add chokes, etc.
Some are easy, like adding caps, cutting traces to install chokes.

ANY EMI can cause 'weird' stuff to happen so don't be fooled thinking it's the PICs fault. Use a scope and see what/where the EMI is. Noisy power supply ? Use a linear based one or add a LOT of filtering to the switcher.

NO amount of 'clever code' will ever fix a hardware EMI problem.

hth
Jay
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