System Reset and Initialization
2-3System Resets, Interrupts, and Operating Modes
2.1.1 Brownout Reset (BOR)
All MSP430x4xx devices have a brownout reset circuit. The brownout reset
circuit detects low supply voltages such as when a supply voltage is applied
to or removed from the VCC terminal. The brownout reset circuit resets the
device by triggering a POR signal when power is applied or removed. The
operating levels are shown in Figure 22.
The POR signal becomes active when VCC crosses the VCC(start) level. It
remains active until VCC crosses the V(B_IT+) threshold and the delay t(BOR)
elapses. The delay t(BOR) is adaptive being longer for a slow ramping VCC. The
hysteresis Vhys(B_ IT) ensures that the supply voltage must drop below
V(B_IT) to generate another POR signal from the brownout reset circuitry.
Figure 22. Brownout Timing
t(BOR)
VCC(start)
VCC
V(B_IT)
Set Signal for
POR circuitry
V
V(B_IT+)
hys(B_IT)
As the V(B_IT) level is significantly above the V(MIN) level of the POR circuit,
the BOR provides a reset for power failures where VCC does not fall below
V(MIN). See device-specific datasheet for parameters.