User Manual
226
Rev. 1.1
2019-03-18
TLE984xQX
Microcontroller with LIN and Power Switches for Automotive Applications
System Control Unit - Power Modules (SCU-PM)
• check of TFILT_CLK = clock used for digital filters: derived out of
f
sys
by configurable division factors
ICU (Interrupt Control Unit)
• PREWARN_SUP_NMI = generation of Prewarn-Supply NMI
• PREWARN_CLK_INT = generation of Prewarn-Clock Watchdog NMI
• INT = generation of MISC interrupts
8.3
Clock Watchdog Unit (CWU)
There are two clock watchdogs available. One main purpose of them, is to monitor the derived switched
capacitor clocks, which are used for analog module operation. If the clocks are not in the required range, a
proper functionality of those modules is not given.
The following chapter describes the functionality and the configuration possibilities of these clock watchdogs.
8.3.1
Fail Safe Functionality of Clock Generation Unit (Clock Watchdog)
The Clock Generation Unit provides also fail safe functionalities, which are related to the input clock, the
generated clocks and the clock settings. Those are:
•
MI_CLK
and
TFILT_CLK
are out of Range: MI Clock settings for f
sys
, MI_CLK and TFILT_CLK Clock settings
are out of required range and as a result the analog functionalities cannot be guaranteed. This failure
triggers the clock watchdog NMI. The current status can be seen in the corresponding registers APCLK1 (in
SCU) for the
MI_CLK
and APCLK2 (in SCU) for the
TFILT_CLK
.
•
Loss of clock:
When there is a loss of clock in the system, there is no possibility for the software to react
upon this situation, like to enter a fail safe mode or switch to another backup clock source. For this purpose
there is a clock watchdog implemented in the system which monitors the f
sys
and in case of this emergency
situation, disables all critical system functions, which are:
– Low Sides
– High Sides
– LIN
As shown in
all analog clocks are derived from
MI_CLK
. This clock structure requires to place a
monitor on this clock, because f
sys
and therefore
MI_CLK
are adjustable in a wide range (see also Chapter
System Control Unit - CGU
). As an important clock, also the TFILT_CLK is monitored by a clock watchdog.
This clock watchdogs have an adjustable lower and upper limits including hysteresis. The placement of the
clock watchdogs in the clock structure is sketched below: