6.10 Oscillator Failure Detection; 6.11 Fault Mux Registers Reference - Texas Instruments UCD3138 Technical Reference Manual

Oscillator Failure Detection

6.10 Oscillator Failure Detection

The Fault Mux Module provides the capability to detect failures of the High Frequency and Low Frequency
Oscillator blocks. Detection of a High Frequency Oscillator failure can be configured to generate a chip
reset. Firmware can configure the Fault Mux Module to generate an interrupt upon detection of a Low
Frequency Oscillator Failure.
6.10.1 High Frequency Oscillator Failure Detection
Two counters are used to detect a failure with the High Frequency Oscillator block. One counter is
implemented in the High Frequency Oscillator clock domain, while the other counter is implemented in the
Low Frequency Oscillator clock domain. The High Frequency Oscillator counter generates a clear signal
once the counter reaches a firmware programmable 17-bit threshold. This clear signal clears the free
running Low Frequency Oscillator counter. In the case of a High Frequency Oscillator failure, no clear
signal is generated and the Low Frequency Oscillator counter will overflow, generating an oscillator fail
flag to the SYS module. Based on the SYS module setup, a chip reset may be generated from the
oscillator failure.
There are 2 bitfields in the HFO Failure detection register HFOFAILDET.
HFO_FAIL_THRESH – Configures threshold where a clear flag is used to clear a counter in the Low
Frequency Oscillator domain (if LFO counter overflows, a reset will be generated), resolution of threshold
equals High Frequency Oscillator perio
Bit 0: HFO_DETECT_EN – a 1 enables High Frequency Oscillator Failure Detection logic, device will be
reset upon detection of an oscillator failure .
here is no interrupt or status bit for HFO failure. This is because if the HFO fails, the processor will not be
working.
6.10.2 Low Frequency Oscillator Failure Detection
The Low Frequency Oscillator is used for the watchdog timer, and to test the functionality of the HFO as
described above. As with the High Frequency Oscillator Failure detection, two counters are used to detect
a failure with the Low Frequency Oscillator block. The counter roles are reversed in the Low Frequency
Oscillator failure detection with the Low Frequency Oscillator clock generating a clear signal once the
counter reaches a firmware programmable 5-bit threshold. This clear signal clears the free running High
Frequency Oscillator counter. In the case of a Low Frequency Oscillator failure, no clear signal is
generated and the High Frequency Oscillator counter will overflow. Firmware can detect the Low
Frequency Oscillator Failure through the Fault Mux interrupt or through polling the status register in the
Fault Mux Registers. There are three bit fields in the LFOFAILDET register:
• LFO_FAIL_THRESH – Configures threshold where a clear flag is used to clear a counter in the High
Frequency Oscillator domain (if HFO counter overflows, a reset will be generated), resolution of
threshold equals Low Frequency Oscillator period
• LFO_FAIL_INT_EN – a 1 enables Interrupt Generation upon LFO Failure Detection
• LFO_DETECT_EN – a 1 enables the LFO failure detection circuitry.
There are LFO_FAIL bits in the FAULTMUXRAWSTAT and FAULTMUXINTSTAT registers, giving status
of the LFO fault detection status and interrupt status.

6.11 Fault Mux Registers Reference

6.11.1 Analog Comparator Control 0 Register (ACOMPCTRL0)
Address 00030000
234
Fault Mux
Copyright © 2016, Texas Instruments Incorporated
SNIU028A – February 2016 – Revised April 2016
Submit Documentation Feedback
www.ti.com