LM3S308 Luminary Micro, Inc, LM3S308 Datasheet - Page 59

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

6.2
6.3
Table 6-1. System Control Register Map
June 04, 2008
Offset
0x01C
0x000
0x004
0x008
0x010
0x014
0x018
0x030
0x034
0x040
0x044
Name
DID0
DID1
DC0
DC1
DC2
DC3
DC4
PBORCTL
LDOPCTL
SRCR0
SRCR1
Initialization and Configuration
The PLL is configured using direct register writes to the RCC register. The steps required to
successfully change the PLL-based system clock are:
1.
2.
3.
4.
5.
Note:
Register Map
Table 6-1 on page 59 lists the System Control registers, grouped by function. The offset listed is a
hexadecimal increment to the register’s address, relative to the System Control base address of
0x400F.E000.
Note:
Bypass the PLL and system clock divider by setting the BYPASS bit and clearing the USESYS
bit in the RCC register. This configures the system to run off a “raw” clock source (using the
main oscillator or internal oscillator) and allows for the new PLL configuration to be validated
before switching the system clock to the PLL.
Select the crystal value (XTAL) and oscillator source (OSCSRC), and clear the PWRDN and OEN
bits in RCC. Setting the XTAL field automatically pulls valid PLL configuration data for the
appropriate crystal, and clearing the PWRDN and OEN bits powers and enables the PLL and its
output.
Select the desired system divider (SYSDIV) in RCC and set the USESYS bit in RCC. The SYSDIV
field determines the system frequency for the microcontroller.
Wait for the PLL to lock by polling the PLLLRIS bit in the Raw Interrupt Status (RIS) register.
Enable use of the PLL by clearing the BYPASS bit in RCC.
If the BYPASS bit is cleared before the PLL locks, it is possible to render the device unusable.
Spaces in the System Control register space that are not used are reserved for future or
internal use by Luminary Micro, Inc. Software should not modify any reserved memory
address.
Type
R/W
R/W
R/W
R/W
RO
RO
RO
RO
RO
RO
RO
0xBFFF.00C0
0x0001.72BF
0x0000.7FFD
0x0107.1013
0x0000.001F
0x0000.0000
0x000F.0007
0x00000000
0x00000000
Reset
-
-
Preliminary
Description
Device Identification 0
Device Identification 1
Device Capabilities 0
Device Capabilities 1
Device Capabilities 2
Device Capabilities 3
Device Capabilities 4
Power-On and Brown-Out Reset Control
LDO Power Control
Software Reset Control 0
Software Reset Control 1
LM3S308 Microcontroller
page
See
106
107
61
78
80
81
83
85
87
63
64
59