LM3S5K36 Datasheet, PDF (188/1050 Pages) Texas Instruments – Stellaris® LM3S5K36 Microcontroller

System Control
Figure 5-3. Reset Circuit Controlled by Switch
VDD
Stellaris®
R_PU
RST
R_S
C₁
5.2.2.4
5.2.2.5
Typical R_PU = 10 kΩ
Typical R_S = 470 Ω
C₁ = 10 nF
The R_PU and C₁ components define the power-on delay.
The external reset timing is shown in Figure 24-7 on page 990.
Brown-Out Reset (BOR)
The microcontroller 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 an interrupt or a system reset. The default condition is to generate an interrupt, so
BOR must be enabled. 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; if BORIOR is clear, an interrupt is generated. When a Brown-out condition
occurs during a Flash PROGRAM or ERASE operation, a full system reset is always triggered
without regard to the setting in the PBORCTL register.
The brown-out reset sequence is as follows:
1. When V_DD drops below V_BTH, an internal BOR condition is set.
2. If the BOR condition exists, an internal reset is asserted.
3. The internal reset is released and the microcontroller fetches and loads the initial stack pointer,
the initial program counter, the first instruction designated by the program counter, and begins
execution.
4. The internal BOR condition is reset after 500 µs to prevent another BOR condition from being
set before software has a chance to investigate the original cause.
The result of a brown-out reset is equivalent to that of 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 handler to determine if a Brown-Out condition was the cause of the reset, thus
allowing software to determine what actions are required to recover.
The internal Brown-Out Reset timing is shown in Figure 24-5 on page 989.
Software Reset
Software can reset a specific peripheral or generate a reset to the entire microcontroller.
188
January 21, 2012
Texas Instruments-Production Data