If you intend to blow the fuse and your device has a UART interface,
then it is a good idea to connect the BSL RX and TX pins in parallel to
the UART pins you use, on your device.
Then you can fix broken devices (flash checksum error) by reloading the
firmware with BSL. You will also need the reset pin and one of the JTAG
pins to do it. If your host supports handshaking signals, you can use
them to implement the BSL. There are ANs from TI describing that in
great detail. You can prepare those connections on your device.
You will not be able to use JTAG once the fuse has been blown, which
means you cannot debug/develop on a device with blown fuse. This applies
to reverse engineering as well. By the way, the energy to burn the fuse
is rather small, we do it with a charged capacitor and a bootstrap circuit.
For our devices we also separated system and application functions of
the firmware, so we can update the application part of the firmware
using the UART interface with the standard host protocol. For a version
upgrade we don't have to take the device out of the host environment.
Only if the problem is in the (small) system part, the device does not
boot normally and we have to boot into BSL.
Regards,
D. Teuchert
[email protected] wrote:
Message: 2
Date: Wed, 25 Jun 2008 14:53:27 -0500
From: "TonyB" <[email protected]>
Subject: [Mspgcc-users] JTAG Security Fuse
To: "GCC for MSP430 - http://mspgcc.sf.net";
<[email protected]>
Message-ID: <004c01c8d6fd$28943290$32fea...@gateway>
Content-Type: text/plain; charset="iso-8859-1"
We're looking into using the JTAG security fuse in our product to prevent snooping (namely to safeguard an encryption key).
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