LM3S2948 Datasheet, PDF (168/686 Pages) Texas Instruments – Stellaris® LM3S2948 Microcontroller

System Control
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 168 and Table 5-2 on page 168 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 291. 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 305) should be set to choose the NMI function. For more information on configuring
GPIOs, see “General-Purpose Input/Outputs (GPIOs)” on page 282. 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.
Table 5-2. System Control & Clocks Signals (108BGA)
Pin Name
Pin Number Pin Type Buffer Type^a Description
CMOD0
E11
I
TTL
CPU Mode bit 0. Input must be set to logic 0 (grounded); other
encodings reserved.
CMOD1
B10
I
TTL
CPU Mode bit 1. Input must be set to logic 0 (grounded); other
encodings reserved.
OSC0
L11
I
Analog Main oscillator crystal input or an external clock reference
input.
OSC1
M11
O
Analog Main oscillator crystal output. Leave unconnected when using
a single-ended clock source.
RST
H11
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 169)
168
June 18, 2012
Texas Instruments-Production Data