LM3S1636_13 Datasheet, PDF (166/655 Pages) Texas Instruments – Stellaris Microcontroller

System Control
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5 System Control
System control determines the overall operation of the device. It provides information about the
device, controls the clocking to the core and individual peripherals, and handles reset detection and
reporting.
5.1 Signal Description
Table 5-1 on page 166 list the external signals of the System Control module and describe the function
of each. The NMI signal is the alternate function for and functions as a GPIO after reset. under
commit protection and require a special process to be configured as any alternate function or to
subsequently return to the GPIO function, see “Commit Control” on page 287. The column in the
table below titled "Pin Assignment" lists the GPIO pin placement for the NMI signal. The AFSEL bit
in the GPIO Alternate Function Select (GPIOAFSEL) register (page 301) should be set to choose
the NMI function. For more information on configuring GPIOs, see “General-Purpose Input/Outputs
(GPIOs)” on page 280. The remaining signals (with the word "fixed" in the Pin Assignment column)
have a fixed pin assignment and function.
Table 5-1. System Control & Clocks Signals (100LQFP)
Pin Name
Pin Number Pin Type Buffer Type^a Description
CMOD0
65
I
TTL
CPU Mode bit 0. Input must be set to logic 0 (grounded); other
encodings reserved.
CMOD1
76
I
TTL
CPU Mode bit 1. Input must be set to logic 0 (grounded); other
encodings reserved.
OSC0
48
I
Analog Main oscillator crystal input or an external clock reference
input.
OSC1
49
O
Analog Main oscillator crystal output. Leave unconnected when using
a single-ended clock source.
RST
64
I
TTL
System reset input.
a. The TTL designation indicates the pin has TTL-compatible voltage levels.
5.2 Functional Description
The System Control module provides the following capabilities:
■ Device identification (see “Device Identification” on page 166)
■ Local control, such as reset (see “Reset Control” on page 166), power (see “Power
Control” on page 170) and clock control (see “Clock Control” on page 171)
■ System control (Run, Sleep, and Deep-Sleep modes); see “System Control” on page 177
5.2.1
Device Identification
Several read-only registers provide software with information on the microcontroller, such as version,
part number, SRAM size, flash size, and other features. See the DID0, DID1, and DC0-DC4 registers.
5.2.2
Reset Control
This section discusses aspects of hardware functions during reset as well as system software
requirements following the reset sequence.
166
July 24, 2012
Texas Instruments-Production Data