Datasheet

5 System Control
System control configures the overall operation of the device and provides information about the
device. Configurable features include reset control, NMI operation, power control, clock control, and
low-power modes.
5.1 Signal Description
The following table lists the external signals of the System Control module and describes the function
of each. The NMI signal is the alternate function for two GPIO signals, which default to GPIO after
reset. The NMI pins are 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 760 for more information. The column in the table below titled "Pin Mux/Pin
Assignment" lists the GPIO pin placement for the NMI signal. The number in parentheses next to
the pin placement listed is the encoding that must be programmed into the PMCn field in the GPIO
Port Control (GPIOPCTL) register (page 795) to assign the NMI signal to the specified GPIO port
pin. In addition, the AFSEL bit in the GPIO Alternate Function Select (GPIOAFSEL) register
(page 778) should be set to choose the NMI function. For more information on configuring GPIOs,
see “General-Purpose Input/Outputs (GPIOs)” on page 750. The remaining signals listed in the table
(with the word "fixed" in the Pin Mux/Pin Assignment column) have a fixed pin assignment and
function.
Table 5-1. System Control & Clocks Signals (128TQFP)
DescriptionBuffer TypePin TypePin Mux / Pin
Assignment
Pin NumberPin Name
An optionally divided reference clock output based
on a selected clock source. Note that this signal is
not synchronized to the System Clock.
TTLOPQ4 (7)102DIVSCLK
Non-maskable interrupt.TTLIPD7 (8)128NMI
Main oscillator crystal input or an external clock
reference input.
AnalogIfixed88OSC0
Main oscillator crystal output. Leave unconnected
when using a single-ended clock source.
AnalogOfixed89OSC1
System reset input.TTLIfixed70RST
5.2 Functional Description
The System Control module provides the following capabilities:
■ Device identification, see “Device Identification” on page 227
■ Configurable control of reset, power, and clock sources.
■ System control (Run, Sleep, and Deep-Sleep modes), see “System Control” on page 246
5.2.1 Device Identification
Read-only registers in the system control module provide information about the microcontroller,
such as version, part number, pin count, operating temperature range and available peripherals on
the device. The Device Identification 0 (DID0) (page 262) and Device Identification 1 (DID1)
(page 264) registers provide details about the device's version, package, temperature range, and so
on. The Peripheral Present registers starting at system control offset 0x300, such as the Watchdog
227June 18, 2014
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TM4C129ENCPDT Microcontroller