LM3S2139 Luminary Micro, Inc, LM3S2139 Datasheet - Page 58

• Manufacturer Part Number: LM3S2139
• Description: Lm3s2139 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

System Control
6
6.1
6.1.1
6.1.2
6.1.2.1
6.1.2.2
6.1.2.3
58
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.
Functional Description
The System Control module provides the following capabilities:
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■
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Device Identification
Seven 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.
Reset Control
This section discusses aspects of hardware functions during reset as well as system software
requirements following the reset sequence.
CMOD0 and CMOD1 Test-Mode Control Pins
Two pins, CMOD0 and CMOD1, are defined for use by Luminary Micro for testing the devices during
manufacture. They have no end-user function and should not be used. The CMOD pins should be
connected to ground.
Reset Sources
The controller has five sources of reset:
1.
2.
3.
4.
5.
After a reset, the Reset Cause (RESC) register is set with the reset cause. The bits in this register
are sticky and maintain their state across multiple reset sequences, except when an internal POR
is the cause, and then all the other bits in the RESC register are cleared except for the POR indicator.
RST Pin Assertion
The external reset pin (RST) resets the controller. This resets the core and all the peripherals except
the JTAG TAP controller (see “JTAG Interface” on page 47). The external reset sequence is as
follows:
Device identification, see “Device Identification” on page 58
Local control, such as reset (see “Reset Control” on page 58), power (see “Power
Control” on page 61) and clock control (see “Clock Control” on page 61)
System control (Run, Sleep, and Deep-Sleep modes), see “System Control” on page 64
External reset input pin (RST) assertion, see “RST Pin Assertion” on page 58.
Power-on reset (POR), see “Power-On Reset (POR)” on page 59.
Internal brown-out (BOR) detector, see “Brown-Out Reset (BOR)” on page 59.
Software-initiated reset (with the software reset registers), see “Software Reset” on page 60.
A watchdog timer reset condition violation, see “Watchdog Timer Reset” on page 60.
Preliminary
July 25, 2008