SLAU320AJ July 2010 – May 2021
Reference function: IsFuseBlown, IsLockKeyProgrammed
After the JTAG Fuse is burned (for 1xx, 2xx, or 4xx devices) or the JTAG Lock Key is programmed (for 5xx or 6xx devices) and a RESET (by the JTAG ExecutePOR command or the RST/NMI pin in hardware) has been issued, the only JTAG function that is available on the target MSP430 is BYPASS. When the target is in BYPASS, data sent from host to target is delayed by one TCK pulse and then output on TDO, where it can be received by other devices downstream of the target MSP430.
To test a device for being protected, access to any JTAG data register can be attempted. In the following communication sequence, the JTAG CNTRL_SIG register is accessed.
Initialize JTAG access (ResetTAP) | ||
IR_SHIFT("IR_CNTRL_SIG_CAPTURE") | ||
DR_SHIFT16(0xAAAA) | ||
Is TDO output value = 0x5555? | ||
Yes: Device IS protected | No: Device NOT protected |