Texas Instruments MSP430x1xx User Manual page 123

Oscillator Fault Detection
Signal XT_OscFault triggers the OFIFG flag as shown in Figure 4−10. The
LFXT1_OscFault signal is low when LFXT1 is in LF mode.
On devices without XT2, the OFIFG flag cannot be cleared when LFXT1 is in
LF mode. MCLK may be sourced by LFXT1CLK in LF mode by setting the
SELMx bits, even though OFIFG remains set.
On devices with XT2, the OFIFG flag can be cleared by software when LFXT1
is in LF mode and it remains cleared. MCLK may be sourced by LFXT1CLK
in LF mode regardless of the state of the OFIFG flag.
Figure 4−10. Oscillator-Fault-Interrupt
XT1off
LFXT1_OscFault
POR
XT2off
XT2_OscFault
XT2
XTS
SELM1
SELM0
DCOR
XT2 Is an internal signal. XT2 = 0 on devices without XT2 (MSP430x11xx and MSP430x12xx).
XT2 = 1 on devices with XT2 (MSP430F13x, MSP430F14x, MSP430F15x, and(MSP430F16x)
IRQA: Interrupt request accepted
LFXT1_OscFault: Only applicable to LFXT1 oscillator in HF mode.
Oscillator Fault Interrupt Request
XT_OscFault
S
IFG1.1
IE1.1 Clear
PUC IRQA
Oscillator Fault Fail-Safe Logic
Fault_from
XT2
Fault_from
XT1
Basic Clock Module Operation
OFIFG
OF_IRQ_NMI
OFIE
Basic Clock Module
XSELM1
XDCOR
4-11