4.2.5.3 Bus Faults
System accesses from the core can receive a bus fault in the following condition(s):
• The core attempts to access an address that is not assigned to any peripheral or other system device. These faults can be enabled
or disabled by setting the ADDRFAULTEN bit appropriately in MSC_CTRL.
• The core attempts to access a peripheral or system device that has its clock disabled. These faults can be enabled or disabled by
setting the CLKDISFAULTEN bit appropriately in MSC_CTRL.
• The bus times out during an access. For example, this could happen while trying to synchronize volatile read data during an LE
peripheral access. See
11.3.1.1 HFCLK - High Frequency Clock
. These faults can be enabled or disabled by setting the TIMEOUT-
FAULTEN bit appropriately in MSC_CTRL.
In addition to any condition-specific bus fault control bits, the bus fault interrupt itself can be enabled or disabled in the same way as all
other internal core interrupts.
Note:
The icache flush is not triggered at the event of a bus fault. As a result, when an instruction fetch results in a bus fault, invalid
data may be cached. This means that the next time the instruction that caused the bus fault is fetched, the processor core will get the
invalid cached data without any bus fault. In order to avoid invalid cached data propagation to the processor core, software should man-
ually invalidate cache by writing 1 to MSC_CMD_INVCACHE bitfield at the event of a bus fault.
4.3 Access to Low Energy Peripherals (Asynchronous Registers)
The Low Energy Peripherals are capable of running when the high frequency oscillator and core system is powered off, i.e. in energy
mode EM2 Deep Sleep and in some cases also EM3 Stop. This enables the peripherals to perform tasks while the system energy con-
sumption is minimal.
The Low Energy Peripherals are listed in
Table 4.3 Low Energy Peripherals on page 47
.
All Low Energy Peripherals are memory mapped, with automatic data synchronization. Because the Low Energy Peripherals are run-
ning on clocks asynchronous to the high frequency system clock, there are some constraints on how register accesses are performed,
as described in the following sections.
Reference Manual
Memory and Bus System
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