
EM358x
Rev. 0.4
39
If an option byte error is detected, the system restarts and the read and check process is repeated. If the error is
detected again the process is repeated but stops on the 3
rd
failure. The system is then placed into an emulated
deep sleep where recovery is possible. In this state, flash memory readout protection is forced active to prevent
secure applications from being compromised.
5.2.1.6
Debug Reset
The Serial Wire/JTAG Interface (SWJ) provides access to the SWJ Debug Port (SWJ-DP) registers. By setting
the register bit CDBGRSTREQ in the SWJ-DP, the reset source CDBGRSTREQ is provided to the Reset
Generation module.
5.2.1.7
JRST
One of the EM358x’s pins can function as the JTAG reset, conforming to the requirements of the JTAG standard.
This input acts independently of all other reset sources and, when asserted, does not reset any on-chip hardware
except for the JTAG TAP. If the EM358x is in the Serial Wire mode or if the SWJ is disabled, this input has no
effect.
5.2.1.8
Deep Sleep Reset
The Power Management module informs the Reset Generation module of entry into and exit from the deep sleep
states. The deep sleep reset is applied in the following states: before entry into deep sleep, while removing power
from the memory and core domain, while in deep sleep, while waking from deep sleep, and while reapplying
power until reliable power levels have been detect by POR LV.
The Power Management module allows a special emulated deep sleep state that retains memory and core
domain power while in deep sleep.
5.2.2
Reset Recording
The EM358x records the last reset condition that generated a restart to the system. The reset conditions recorded
are:
POR HV
always-on domain power supply failure
POR LV
core domain (POR LVcore) or memory domain (POR LVmem) power supply failure
nRESET
pin reset asserted
watchdog
watchdog timer expired
SYSRESETREQ
software reset by SYSERSETREQ from ARM
®
Cortex
TM
-M3 CPU
deep sleep wakeup wake-up from deep sleep
option byte error
error check failed when reading option bytes from flash
Note:
While CPU Lockup is shown as a reset condition in software, CPU Lockup is not specifically a reset event.
CPU Lockup is set to indicate that the CPU entered an unrecoverable exception. Execution stops but a
reset is not applied. This is so that a debugger can interpret the cause of the error. Silicon Labs
recommends that in a live application (in other words, no debugger attached) the watchdog be enabled by
default so that the EM358x can be restarted.
5.2.3
Reset Generation Module
The Reset Generation module responds to reset sources and generates the following reset signals:
PORESET
Reset of the ARM
®
Cortex
TM
-M3 CPU and ARM
®
Cortex
TM
-M3 System Debug components (Flash Patch and
Breakpoint, Data Watchpoint and Trace, Instrumentation Trace Macrocell, Nested Vectored Interrupt
Controller). ARM defines PORESET as the region that is reset when power is applied.
SYSRESET
Reset of the ARM
®
Cortex
TM
-M3 CPU without resetting the Core Debug and System Debug components,
so that a live system can be reset without disturbing the debug configuration.
DAPRESET
Reset to the SWJ’s AHB Access Port (AHB-AP)
PRESET
HV
Peripheral reset for always-on power domain, for peripherals that are required to retain their
configuration across a deep sleep cycle
PRESET
LV
Peripheral reset for core power domain, for peripherals that are not required to retain their
configuration across a deep sleep cycle
Summary of Contents for EMBER EM358 series
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