MSP430 Security Fuse blown

Hi,

can you please try the scripts which i posted here:

http://e2e.ti.com/support/microcontrollers/msp430/f/166/p/183624/662344.aspx#662344

Hi Leo,

Thanks for the thread link.

No where it is mentioned the reason for fuse blown.So can you let me know the causes for the same.

Best Regards,

Santosh.

Santosh PG said:

No where it is mentioned the reason for fuse blown.

"Fuse blown" actually means "Device doesn't respond to JTAG commands".
One porrible reason is indeed a blown fuse which disables JTAG. However, faulty firmware that causes an immediate (and endless) reset cycle may also cause the JTAG connection to be cut as if it were disabled. The debugger cannot distringuish between the two (same behaviour) and therefore gives the fuse error.

Jens-Michael Gross said:

"Fuse blown" actually means "Device doesn't respond to JTAG commands".
One porrible reason is indeed a blown fuse which disables JTAG. However, faulty firmware that causes an immediate (and endless) reset cycle may also cause the JTAG connection to be cut as if it were disabled. The debugger cannot distringuish between the two (same behaviour) and therefore gives the fuse error.

I am also facing the same problem "Security fuse blown" while connecting to the MSP430F5438A on our hardware.

Prior to the last firmware i downloaded in the MCU, it was working fine. The last firmware I downloaded was doing Flash related operations in the the main code memory. My guess is this might have caused the problem.

Can you please tell me what has exactly happened and how to solve it? Because of this problem I am not able to use the board anymore and also do not have any spare MCUs.

Also I would like to know what is this fuse exactly? Can it be fixed if blown?

Regards,

Sanket Garade

sanket garade said:

My guess is this might have caused the problem.

Always possible. If your code doe ssomething that causes the MSP to reset (e.g. an access violation), this may happen while the FET is still attaching. This will sewer the JTAG connection and it looks like the JTAG doesn't respont, as if the fuse were blown.

You may try a different software like the Elprotronic flashing software that is a bit faster. Maybe this small difference in speed allows teh software to attach, stop the CPU before it executes the offending code , and do a mass erase.
If this fails, the other option is to use the BSL to do a mass erase. This requires a different physical connection to the MSP. Sinc eth eBSL is checked and (if requested9 entered before any user code is executed, this will always work.

On the 5438A (and most other 5x family devices) the fuse is a software fuse, a key written to the BSL flash area. It is difficult to mess with it unintentionally. And it can be undone. However, if the JTAG fuse is gone, most likely the BSL is affected too. On olde rMSP, the fuse was a physical thing and blowing it required a high current on a certain pin at  specific moment. It cannot be undone because here the fuse is really blown physically. But then, accidentally blowing it is even more difficult.

However in 99% of all cases, the fuse is intact and faulty user code creates an effect that let it appear to be blown to the FET.

You'll find many threads where detailed information is given about the BSL.

(Hint: 'fuse' and 'BSL' are good keywords for a forum search)