LM3S308 Luminary Micro, Inc, LM3S308 Datasheet - Page 53

• Manufacturer Part Number: LM3S308
• Description: Lm3s308 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

6.1.2.3
6.1.2.4
June 04, 2008
1.
2.
3.
The external reset timing is shown in Figure 19-9 on page 395.
Power-On Reset (POR)
The Power-On Reset (POR) circuitry detects a rise in power-supply voltage (V
an on-chip reset pulse. To use the on-chip circuitry, the RST input needs to be connected to the
power supply (V
The device must be operating within the specified operating parameters at the point when the on-chip
power-on reset pulse is complete. The specified operating parameters include supply voltage,
frequency, temperature, and so on. If the operating conditions are not met at the point of POR end,
the Stellaris
external circuitry. The RST input may be used with the circuit as shown in Figure 6-1 on page 53.
Figure 6-1. External Circuitry to Extend Reset
The R
the RST input. The diode (D
The Power-On Reset sequence is as follows:
1.
2.
3.
The internal POR is only active on the initial power-up of the controller. The Power-On Reset timing
is shown in Figure 19-10 on page 396.
Note:
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 external reset pin (RST) is asserted and then de-asserted.
After RST is de-asserted, the main crystal oscillator is allowed to settle and there is an internal
main oscillator counter that takes from 15-30 ms to account for this. During this time, internal
reset to the rest of the controller is held active.
The internal reset is released and the core fetches and loads the initial stack pointer, the initial
program counter, the first instruction designated by the program counter, and begins execution.
The controller waits for the later of external reset (RST) or internal POR to go inactive.
After the resets are inactive, the main crystal oscillator is allowed to settle and there is an internal
main oscillator counter that takes from 15-30 ms to account for this. During this time, internal
reset to the rest of the controller is held active.
The internal reset is released and the core fetches and loads the initial stack pointer, the initial
program counter, the first instruction designated by the program counter, and begins execution.
D
1
1
and C
The power-on reset also resets the JTAG controller. An external reset does not.
R
®
C
1
controller does not operate correctly. In this case, the reset must be extended using
1
1
components define the power-on delay. The R
R
DD
2
) through a pull-up resistor (1K to 10K Ω).
RST
1
) discharges C
Stellaris
Preliminary
1
rapidly when the power supply is turned off.
2
resistor mitigates any leakage from
LM3S308 Microcontroller
DD
) and generates
53