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CS Registers
3.4.5 CSCTL4 Register
Clock System Control 4 Register
Figure 3-9. CSCTL4 Register
15
14
13
12
11
10
9
8
XT2DRIVE
Reserved
XT2BYPASS
Reserved
XT2OFF
rw-1
rw-1
r0
rw-0
r0
r0
r0
rw-1
7
6
5
4
3
2
1
0
XT1DRIVE
XTS
XT1BYPASS
Reserved
SMCLKOFF
XT1OFF
rw-1
rw-1
rw-0
rw-0
r0
r0
rw-0
rw-1
Table 3-7. CSCTL4 Register Description
Bit
Field
Type
Reset
Description
15-14
XT2DRIVE
RW
3h
The XT2 oscillator current can be adjusted to its drive needs.
00b = Lowest current consumption. XT2 oscillator operating range is 4 MHz to 8
MHz.
01b = Increased drive strength XT2 oscillator. XT2 oscillator operating range is 8
MHz to 16 MHz.
10b = Increased drive capability XT2 oscillator. XT2 oscillator operating range is
16 MHz to 24 MHz.
11b = Maximum drive capability and maximum current consumption for both XT2
oscillator. XT2 oscillator operating range is 24 MHz to 32 MHz.
13
Reserved
R
0h
Reserved. Always reads as 0.
12
XT2BYPASS
RW
0h
XT2 bypass select
0b = XT2 sourced from external crystal
1b = XT2 sourced from external clock signal
11-9
Reserved
R
0h
Reserved. Always reads as 0.
8
XT2OFF
RW
1h
Turns off the XT2 oscillator
0b = XT2 is on if XT2 is selected by the port selection and XT2 is not in bypass
mode of operation.
1b = XT2 is off if it is not used as a source for ACLK, MCLK, or SMCLK
7-6
XT1DRIVE
RW
3h
The XT1 oscillator current can be adjusted to its drive needs.
00b = Lowest current consumption for XT1 LF mode. XT1 oscillator operating
range in HF mode is 4 MHz to 8 MHz.
01b = Increased drive strength for XT1 LF mode. XT1 oscillator operating range
in HF mode is 8 MHz to 16 MHz.
10b = Increased drive capability for XT1 LF mode. XT1 oscillator operating range
in HF mode is 16 MHz to 24 MHz.
11b = Maximum drive capability and maximum current consumption for XT1 LF
mode. XT1 oscillator operating range in HF mode is 24 MHz to 32 MHz.
5
XTS
RW
0h
XT1 mode select
0b = Low-frequency mode
1b = High-frequency mode
4
XT1BYPASS
RW
0h
XT1 bypass select
0b = XT1 sourced from external crystal
1b = XT1 sourced from external clock signal
3-2
Reserved
R
0h
Reserved. Always reads as 0.
1
SMCLKOFF
RW
0h
SMCLK off. This bit turns off the SMCLK.
0b = SMCLK on
1b = SMCLK off
0
XT1OFF
RW
1h
XT1 off. This bit turns off the XT1.
0b = XT1 is on if XT1 is selected by the port selection and XT1 is not in bypass
mode of operation
1b = XT1 is off if it is not used as a source for ACLK, MCLK, or SMCLK
84
Clock System (CS)
SLAU272C – May 2011 – Revised November 2013
Copyright © 2011–2013, Texas Instruments Incorporated