MCU Device Reset Reasons

The Microcontroller’s RCON register contains details of the most recent reset / power-on event and is exposed via the USB and I²C interfaces. See the PIC32MM0256GPM028 datasheet for details on how to interpret this register.

Note that if bit 15 is set (0x00008000) then the reset reason can be interpreted as a firmware-induced reset rather than a hardware-based fault event. The reasons the firmware can cause a reset are:

Code	Reason	Description
0x8XXX8XXX	Safe Mode Indicator	The device probably requires re-flashing if you get this. It’s limping along with a default configuration (tri-stated pins).
0xX0008001	General Exception Handler	See the MCU Exception Details section below for extra debugging information.
0xX0008041	Free RTOS Assertion Failure	Basically a firmware bug. Difficult to track down without a debugger.
0xX0008042	Free RTOS Stack Overflow	Basically a firmware bug. Difficult to track down without a debugger.
0xX0008043	Memory Allocation Error	Basically a firmware bug. Difficult to track down without a debugger.
0xX0008080	Configuration Updated	Configuration has been updated successfully and the device reset.
0xX000808X	Configuration Failure	Some sort of configuation issue, possibly Flash corruption. The exact number depends on the assertion in Configuration.c.

During some resets, snapshots of the Microcontroller’s ERROREPC, EPC, CAUSE, DESAVE and RA registers are also captured and are exposed.

MCU Exception Details

For MCU general exceptions as well as FreeRTOS assertion, malloc and stack overflow failures, the MCU’s ERROREPC, EPC, CAUSE, DESAVE and RA registers are persisted through the reset to allow retrieval for debugging. The values of the registers immediately before the reset can be retrieved via the I²C Device Information Bank or with the USB Device Status command, presuming the system manages to boot that far.