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We are making a production product using the MSP430G2231 and want to keep the code a secret.

I have searched online and found out that blowing the security fuse disables access to the MCU.

Could somebody please clarify that by giving 6 and 7 V (100mA) for at least 1ms to the TEST pin we can blow the JTAG security fuse? Is this the right way to do it?

David
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Shruthi Chary
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  • There are many ways to "blow" the "security" fuse, but there is only one way that doesn't "blow" any other parts of the chip. Do you have a datasheet for that microcontroller? – jippie Aug 21 '14 at 06:37

2 Answers2

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According to TI appnote SLAU320 the fuse is blown by applying Vpp to TEST pin: enter image description here

But later down in the document it also says this in a subsection of the reference 1.4.1:

enter image description here

Which indicates that you apply the Vpp voltage, then setup the fuse blowing by writing on the JTAG interface. The IR_PREPARE_BLOW and IR_EX_BLOW are described in the document.

Dejvid_no1
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According to:

MSP Code Protection Features

http://www.ti.com/lit/an/slaa685/slaa685.pdf

MSP430F1xx, F2xx, and F4xx family devices JTAG can be secured through a physical JTAG security fuse. The fuse is blown by the programming tool after JTAG or SBW programming. The tool applies a fuse blowing voltage (6.5 V ±0.5 V) on the TEST pin (on devices with a TEST pin) or TDI pin (on devices without a TEST pin) [see MSP430 Programming Via the JTAG Interface (SLAU320)] for more details. Blowing the fuse completely disables the JTAG port and is not reversible, and further JTAG or SBW access is not possible. After the physical fuse is blown, the device is accessible only through the password-protected bootloader, if supported and enabled.

enter image description here

Read this document in detail, it discuss a lot of different variation on the e-fuse implementations among the different families of MSP430 (eg, voltage level)

And take note: even after the fuse is blown, there are still ways to access or read the code:

Is there a way to prevent code being read from an MSP430 without blowing the fuse?

Community
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Peter Teoh
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