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2014-07-02 - Tiny Gecko Family - d0034_Rev1.20
87
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Table 9.1. RMU Reset Cause Register Interpretation
Register Value
Cause
0bXXX XXXX XXX1
A Power-on Reset has been performed. X bits are don't care.
0bXXX 0XXX XX10
A Brown-out has been detected on the unregulated power.
0bXXX XXX0 0100
A Brown-out has been detected on the regulated power.
0bXXX XXXX 1X00
An external reset has been applied.
0bXXX XXX1 XX00
A watchdog reset has occurred.
0bXXX XX10 0000
A lockup reset has occurred.
0b000 01X0 0000
A system request reset has occurred.
0b000 1XX0 0XX0
The system has woken up from EM4.
0b001 1XX0 0XX0
The system has woken up from EM4 on an EM4 wakeup reset request from pin.
0b010 0000 0000
A Brown-out has been detected on Analog Power Domain 0 (AVDD0).
0b100 0000 0000
A Brown-out has been detected on Analog Power Domain 1 (AVDD1).
Note
When exiting EM4 with external reset, both the BODREGRST and BODUNREGRST in
RSTCAUSE might be set (i.e. are invalid)
9.3.2 Power-On Reset (POR)
The POR ensures that the EFM32TG does not start up before the supply voltage V
DD
has reached
the threshold voltage VPORthr (see Device Datasheet Electrical Characteristics for details). Before the
threshold voltage is reached, the EFM32TG is kept in reset state. The operation of the POR is illustrated
in Figure 9.2 (p. 87) , with the active low POWERONn reset signal. The reason for the “unknown”
region is that the corresponding supply voltage is too low for any reliable operation.
Figure 9.2. RMU Power-on Reset Operation
POWERONn
V
DD
t im e
V
Unknown
VPORt hr
9.3.3 Brown-Out Detector Reset (BOD)
The EFM32TG has 4 brownout detectors, one for the unregulated 3.0 V power, one for the regulated
internal power, one for Analog Power Domain 0 (AVDD0), and one for Analog Power Domain 1 (AVDD1).
The BODs are constantly monitoring the voltages. Whenever the unregulated or regulated power drops
below the VBODthr value (see Electrical Characteristics for details), or if the AVDD0 or AVDD1 drops
below the voltage at the decouple pin (DEC), the corresponding active low BROWNOUTn line is held
low. The BODs also include hysteresis, which prevents instability in the corresponding BROWNOUTn
line when the supply is crossing the VBODthr limit or the AVDD bods drops below decouple pin (DEC).
The operation of the BOD is illustrated in Figure 9.3 (p. 88) . The “unknown” regions are handled
by the POR module.
Summary of Contents for EFM32TG
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