LM3S6918 Luminary Micro, Inc, LM3S6918 Datasheet - Page 79

• Manufacturer Part Number: LM3S6918
• Description: Lm3s6918 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

July 26, 2008
Bit/Field
9:6
5:4
11
10
OSCSRC
BYPASS
reserved
Name
XTAL
Type
R/W
R/W
R/W
RO
Reset
0xB
0x1
1
0
Preliminary
Description
PLL Bypass
Chooses whether the system clock is derived from the PLL output or
the OSC source. If set, the clock that drives the system is the OSC
source. Otherwise, the clock that drives the system is the PLL output
clock divided by the system divider.
Note:
Software should not rely on the value of a reserved bit. To provide
compatibility with future products, the value of a reserved bit should be
preserved across a read-modify-write operation.
Crystal Value
This field specifies the crystal value attached to the main oscillator. The
encoding for this field is provided below.
Oscillator Source
Picks among the four input sources for the OSC. The values are:
Value
Value
0x0
0x1
0x2
0x3
0xC
0xD
0xA
0xB
0xE
0xF
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
Input Source
Main oscillator
Internal oscillator (default)
Internal oscillator / 4 (this is necessary if used as input to PLL)
30 KHz internal oscillator
The ADC must be clocked from the PLL or directly from a
14-MHz to 18-MHz clock source to operate properly. While
the ADC works in a 14-18 MHz range, to maintain a 1 M
sample/second rate, the ADC must be provided a 16-MHz
clock source.
Crystal Frequency (MHz)
Not Using the PLL
1.8432
2.4576
1.000
2.000
6 MHz (reset value)
3.579545 MHz
3.6864 MHz
4.9152 MHz
7.3728 MHz
4.096 MHz
6.144 MHz
8.192 MHz
5.12 MHz
4 MHz
5 MHz
8 MHz
LM3S6918 Microcontroller
Crystal Frequency (MHz)
Using the PLL
reserved
reserved
reserved
reserved
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