&gt; That said, I&#x27;m really surprised that JTAG couldn&#x27;t read out the ROM, in theory that is how you would program it.<p>I&#x27;m no embedded expert, but I would <i>assume</i> some devices let you write to them and upload new code using the JTAG interface, but still prevent you from reading if the author have signalled that he wants his code protected.<p>Quick DDGing seems to suggest this is indeed a vendor&#x2F;chip-specific capability:<p><a href="https:&#x2F;&#x2F;duckduckgo.com&#x2F;?q=jtag+read+protection&amp;t=ffsb" rel="nofollow">https:&#x2F;&#x2F;duckduckgo.com&#x2F;?q=jtag+read+protection&amp;t=ffsb</a>