MCUCSR – MCU Control and Status Register

The MCU Control and Status Register provides information on which reset source caused an MCU Reset.

When using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be used. When addressing I/O Registers as data space using LD and ST instructions, 0x20 must be added to these offset addresses.

.
Name:
MCUCSR
Offset:
0x34
Reset:
0x00
Access:
When addressing I/O Registers as data space the offset address is 0x54
Bit76543210
WDRFBORFEXTRFPORF
AccessR/WR/WR/WR/W
Reset0000

Bit 3 – WDRF: Watchdog Reset Flag

Watchdog Reset Flag

This bit is set if a Watchdog Reset occurs. The bit is reset by a Power-on Reset, or by writing a logic zero to the flag.

Bit 2 – BORF: Brown-out Reset Flag

Brown-out Reset Flag

This bit is set if a Brown-out Reset occurs. The bit is reset by a Power-on Reset, or by writing a logic zero to the flag.

Bit 1 – EXTRF: External Reset Flag

External Reset Flag

This bit is set if an External Reset occurs. The bit is reset by a Power-on Reset, or by writing a logic zero to the flag.

Bit 0 – PORF: Power-on Reset Flag

Power-on Reset Flag

This bit is set if a Power-on Reset occurs. The bit is reset only by writing a logic zero to the flag. To make use of the Reset Flags to identify a reset condition, the user should read and then reset the MCUCSR as early as possible in the program. If the register is cleared before another reset occurs, the source of the reset can be found by examining the Reset Flags.