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Blown eFUSEs and disabling reading

Question asked by Mark Butcher on May 1, 2020
Latest reply on May 12, 2020 by Victor Jimenez

HI All

 

I have a question about blown eFUSEs.
They are described as 'intact' when '0' and as 'blown' when '1'. Does this mean that if some setting is set by blowing the eFUSE it can never be removed again? (that is, fuses can be blown once and not set back to the intact state?)

 

There are however not just switch settings but also values - eg. MAC address; if a MAC address of 00-00-00-00-00-01 were to be programmed will it later be possible to change it to 00-00-00-00-00-03 (blowing a second bit?`)

 

If a setting has been block that disables something, will this be disabled forever? eg. blowing SJC_DISABLE would disable JTAG so that JTAG/SWD debugging would never be possible again?

 

Finally, is it possible to disable eFUSE values being read back externally? Eg. possibly SDP_READ_DISABLE ?

 

Thanks in advance

 

Regards

 

Mark

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