20.3.2.1.9 RESET Cause
Special Function Registers (SFRs) are provided to identify Reset causes, as shown in the Interpretation of RESET Flags table. Multiple Resets can simultaneously occur, leading to the activation of several Reset cause flags.
| Value | Description |
|---|---|
| 0 | Cleared - This flag is cleared in the register |
| 1 | Set - This flag is set in the register |
| U | Undefined - See notes |
| V | Valid - This flag may be set while another flag is currently set |
| MCFLAGSB | MCFLAGSA | RSTFR | Cause | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UPDI | CFD | VREG | CRC | WDT | BOOT | DCLS | EC | DFT | OCD | MCRF | ECRF | UPDIRF | SWRF | WDRF | EXTRF | BORF | PORF | |
| 0 | 0 | U | V | 0 | V | V | 0 | 0 | 0 | V | 0 | 0 | 0 | 0 | 0 | 0 | 1 | POR(1) |
| V | V | U | V | V | V | V | V | V | V | V | V | V | V | V | V | 1 | 0 | BOR(2,3) |
| V | V | V | V | V | V | V | V | V | V | V | V | V | V | V | 1 | V | 0 | External Reset(2,3) |
| V | V | V | V | V | V | V | V | V | V | V | V | V | V | 1 | V | V | 0 | Watchdog Reset(1,2) |
| V | V | V | V | V | V | V | V | V | V | V | V | V | 1 | V | V | V | 0 | Software Reset(2,3) |
| V | V | V | V | V | V | V | V | V | V | V | V | 1 | V | V | V | V | 0 | UPDI Reset(2,3) |
| V | V | V | V | V | V | V | V | V | V | V | 1 | V | V | V | V | V | 0 | Error Controller Reset(2,3) |
| V | V | V | V | V | V | V | V | V | V | 1 | V | V | V | V | V | V | 0 | Machine Check Reset |
Note:
- An error may be detected during the boot process after the initial Reset, causing MCRF to be set and MCFLAGS to identify the source. MCRF will also be set if the only MCFLAG set is VREG, which has an UNDEFINED value. In this case, MCRF should also be considered UNDEFINED.
- An error may be detected during the boot process after the initial Reset, causing MCRF to be set and the MCFLAGS to identify the source.
- MCFLAGSA and MCFLAGSB are only valid if MCRF in RSTFR is set.