Texas Instruments MSP430x1xx - Manual (Page 105)

LFXT1 and XT2 Oscillators
7-5
Basic Clock Module
Figure 7–3. Off Signals for the LFXT1 Oscillator
XT2
XTS
OscOff
CPUOff
SELM.1
SELM.0
SCG1
SELS
XT2 Is an Internal Signal
XT2 = 0: MSP430x11x, MSP430x11x1 devices
XT2 = 1: MSP430F13x, MSP430F14x devices
OscOff
0
1
1
CPUOff
x
0
x
SELM.x
x
3 or 2+3 †
x
SCG1
x
x
0
SELS
x
x
1
LFXT1CLK
on
on ‡
on ‡
Comment
Oscillator Active
Clock Signal Needed For MCLK
Clock Signal Needed For SMCLK
† Two oscillators: SELM.x = 3. Three oscillators: SELM.x = 3 and 2
‡ LFXT1CLK is switched off for all other bit combinations
LFoff
XT1off
7.2.2 XT2 Oscillator
A second oscillator, XT2, is available in MSP430F13x and MSP430F14x de-
vices. XT2 sources XT2CLK, and its characteristics are identical to LFXT1 in
HF mode.
The XT2Off control bit disables the XT2 oscillator if signal XT2CLK is not used
for MCLK or SMCLK. If the CPUOff bit is reset and SELM = 2, XT2CLK sources
MCLK . The XT2CLK sources SMCLK if SCG1 is reset and SELS = 1.
Figure 7–4. Off Signals for Oscillator XT2
XT2Off
CPUOff
SELM.1
SELM.0
SCG1
SELS
XT2Off
OscOff
0
1
1
CPUOff
x
0
x
SELM.x
x
2
x
SCG1
x
x
0
SELS
x
x
1
XT2CLK
on
on †
on †
Comment
Oscillator Active
Clock Signal Needed For MCLK
Clock Signal Needed For SMCLK
† XT2CLK is switched off in all other bit combinations