Figure 6-2. External Circuitry to Extend Power-On Reset
R
PU
= 1 kΩ to 100 kΩ
C
1
= 1 nF to 10 µF
If the application requires the use of an external reset switch, Figure 6-3 on page 65 shows the
proper circuitry to use.
Figure 6-3. Reset Circuit Controlled by Switch
Typical R
PU
= 10 kΩ
Typical R
S
= 470 Ω
C
1
= 10 nF
The R
PU
and C
1
components define the power-on delay.
The external reset timing is shown in Figure 19-5 on page 492.
6.1.2.5 Brown-Out Reset (BOR)
A drop in the input voltage resulting in the assertion of the internal brown-out detector can be used
to reset the controller. This is initially disabled and may be enabled by software.
The system provides a brown-out detection circuit that triggers if the power supply (V
DD
) drops
below a brown-out threshold voltage (V
BTH
). If a brown-out condition is detected, the system may
generate a controller interrupt or a system reset.
Brown-out resets are controlled with the Power-On and Brown-Out Reset Control (PBORCTL)
register. The BORIOR bit in the PBORCTL register must be set for a brown-out condition to trigger
a reset.
The brown-out reset is equivalent to an assertion of the external RST input and the reset is held
active until the proper V
DD
level is restored. The RESC register can be examined in the reset interrupt
65June 22, 2010
Texas Instruments-Production Data
Stellaris® LM3S8530 Microcontroller