Datasheet

55
7682C–AUTO–04/08
AT90CAN32/64/128
When the BOD is enabled, and V
CC
decreases to a value below the trigger level (V
BOT-
in Figure
7-5), the Brown-out Reset is immediately activated. When V
CC
increases above the trigger level
(V
BOT+
in Figure 7-5), the delay counter starts the MCU after the Time-out period t
TOUT
has
expired.
The BOD circuit will only detect a drop in V
CC
if the voltage stays below the trigger level for
longer than t
BOD
given in Table 7-1.
Figure 7-5. Brown-out Reset During Operation
7.1.6 Watchdog Reset
When the Watchdog times out, it will generate a short reset pulse of one CK cycle duration. On
the falling edge of this pulse, the delay timer starts counting the Time-out period t
TOUT
. Refer to
page 57 for details on operation of the Watchdog Timer.
Figure 7-6. Watchdog Reset During Operation
7.1.7 MCU Status Register – MCUSR
The MCU Status Register provides information on which reset source caused an MCU reset.
V
CC
RESET
TIME-OUT
INTERNAL
RESET
V
BOT-
V
BOT+
t
TOUT
CK
CC

Bit 7 6 5 4 3 2 1 0
– – – JTRF WDRF BORF EXTRF PORF MCUSR
Read/Write R R R R/W R/W R/W R/W R/W
Initial Value 0 0 0 See Bit Description