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The instructions being prefixed has two implications:
• The two uppermost bits, 9 and 8, of a 10-bit immediate or direct address embedded in an instruction
are ignored, as they are replaced by bits from the prefix register.
• No sign extension of an embedded immediate is performed for instructions that would normally do so,
as the uppermost bits are provided by the prefix register.
17.4.1.5.9 Reset
Following reset, execution starts at an address corresponding to the value of the same vector input as
used for the sleep instruction. This enables a usage model where the sensor controller is completely
disabled (powered down), and once activated, execution starts directly at an address of a dedicated
handler corresponding to the source that caused the sensor controller to be activated.
Restart functionality is also provided by asserting [AUX_SCE:CTL:RESTART], which immediately disrupts
the instruction flow, causing execution to resume at the handler address selected by the vector input.
The restart functionality does not clear internal registers and flags. Reset does disable an active loop or
prefix.
17.4.1.5.10 Limitations
Due to internal pipelining and minimized register bypass logic, the instructions using R0 as a dedicated
register require special caution.
R0 must not be loaded from memory or register by an instruction immediately preceding any instruction
using R0 as a dedicated register. The affected instructions are ld/st rd,(Rs+R0) and jmp/jsr (R0).
Not observing this rule will cause the previous value of R0 to be used instead of the newly loaded one.
Loading an immediate or the result of any non-memory I/O operation into r0 is perfectly valid and causes
the expected behavior.
17.4.1.6 Sensor Controller Control and Status
Several sensor controller status and debug registers are found in [AUX_SCE]. These registers provide
means for the MCU to control the sensor controller and observe its status:
• Hooks for development and debugging software on the sensor controller
• Observation of internal registers and flags in the sensor controller
• Support for starting, stopping, resetting, and single-stepping of the sensor controller
17.4.1.6.1 Single-Stepping and Debugging the Sensor Controller
To do single-stepping, first suspend the sensor controller by setting [AUX_SCE:CTL:SUSPEND]. Single-
stepping is done by writing 1 to [AUX_SCE:CTL:SINGLE_STEP]. One instruction is executed per write.
Normal program execution is done by clearing [AUX_SCE:CTL:SUSPEND].
Full system real-time operation can be debugged by setting the bit [AUX_SCE:CTL:DBG_FREEZE_EN].
This ensures that the sensor controller and AUX timers are stopped when a debugger halts the system
CPU (configured by default to do so in MCU event fabric).
Because the clocks in the MCU domain are asynchronous to the AUX domain, multi-processor debugging
will not be perfectly real-time.
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SWCU117A–February 2015–Revised March 2015 AUX – Sensor Controller with Digital and Analog Peripherals
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