LM3S308 Luminary Micro, Inc, LM3S308 Datasheet - Page 71

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

June 04, 2008
Bit/Field
26:23
21:14
22
13
12
USESYSDIV
reserved
PWRDN
SYSDIV
Name
OEN
Type
R/W
R/W
R/W
R/W
RO
Reset
0xF
0
0
1
1
Preliminary
Description
System Clock Divisor
Specifies which divisor is used to generate the system clock from the
PLL output.
The PLL VCO frequency is 200 MHz.
When reading the Run-Mode Clock Configuration (RCC) register (see
page 70), the SYSDIV value is MINSYSDIV if a lower divider was
requested and the PLL is being used. This lower value is allowed to
divide a non-PLL source.
Enable System Clock Divider
Use the system clock divider as the source for the system clock. The
system clock divider is forced to be used when the PLL is selected as
the source.
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.
PLL Power Down
This bit connects to the PLL PWRDN input. The reset value of 1 powers
down the PLL. See Table 6-2 on page 73 for PLL mode control.
PLL Output Enable
This bit specifies whether the PLL output driver is enabled. If cleared,
the driver transmits the PLL clock to the output. Otherwise, the PLL
clock does not oscillate outside the PLL module.
Note:
Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
0xC
0xD
0xE
0xF
Divisor (BYPASS=1)
reserved
/2
/3
/4
/5
/6
/7
/8
/9
/10
/11
/12
/13
/14
/15
/16
Both PWRDN and OEN must be cleared to run the PLL.
Frequency (BYPASS=0)
reserved
reserved
reserved
reserved
reserved
reserved
reserved
25 MHz
22.22 MHz
20 MHz
18.18 MHz
16.67 MHz
15.38 MHz
14.29 MHz
13.33 MHz
12.5 MHz (default)
LM3S308 Microcontroller
71