MSP430x22x2, MSP430x22x4
MIXED SIGNAL MICROCONTROLLER
SLAS504B − JULY 2006 − REVISED JULY 2007
78
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
POST OFFICE BOX 1443 • HOUSTON, TEXAS 77251−1443
JTAG fuse check mode
MSP430 devices that have the fuse on the TEST terminal have a fuse check mode that tests the continuity of
the fuse the first time the JTAG port is accessed after a power-on reset (POR). When activated, a fuse check
current, I
TF
, of 1 mA at 3 V, 2.5 mA at 5 V can flow from the TEST pin to ground if the fuse is not burned. Care
must be taken to avoid accidentally activating the fuse check mode and increasing overall system power
consumption.
When the TEST pin is again taken low after a test or programming session, the fuse check mode and sense
currents are terminated.
Activation of the fuse check mode occurs with the first negative edge on the TMS pin after power up or if TMS
is being held low during power up. The second positive edge on the TMS pin deactivates the fuse check mode.
After deactivation, the fuse check mode remains inactive until another POR occurs. After each POR the fuse
check mode has the potential to be activated.
The fuse check current only flows when the fuse check mode is active and the TMS pin is in a low state (see
Figure 28). Therefore, the additional current flow can be prevented by holding the TMS pin high (default
condition).
Time TMS Goes Low After POR
TMS
I
TF
I
TEST
Figure 28. Fuse Check Mode Current, MSP430F22xx
NOTE:
The CODE and RAM data protection is ensured if the JTAG fuse is blown and the 256-bit bootloader
access key is used. Also, see the bootstrap loader section for more information.
