Datasheet

109
XMEGA B [DATASHEET]
8291B–AVR–01/2013
reduce the power consumption compared to the enabled mode, but a fall in the V
CC
level between two positive
edges of the 1kHz ULP oscillator output will not be detected. If a brownout is detected in this mode, the BOD circuit
is set in enabled mode to ensure that the device is kept in reset until V
CC
is above V
BOT
again
The BODACT fuse determines the BOD setting for active mode and idle mode, while the BODPD fuse determines the
brownout detection setting for all sleep modes, except idle mode.
Table 9-3. BOD setting fuse decoding.
9.4.3 External Reset
The external reset circuit is connected to the external RESET pin. The external reset will trigger when the RESET pin is
driven below the
RESET pin threshold voltage, V
RST
, for longer than the minimum pulse period, t
EXT
. The reset will be
held as long as the pin is kept low. The
RESET pin includes an internal pull-up resistor.
Figure 9-5. External reset characteristics.
For external reset characterization data consult the device datasheet.
9.4.4 Watchdog Reset
The watchdog timer (WDT) is a system function for monitoring correct program operation. If the WDT is not reset from
the software within a programmable timout period, a watchdog reset will be given. The watchdog reset is active for one to
two clock cycles of the 2MHz internal oscillator.
BODACT[1:0]/ BODPD[1:0] Mode
00 Reserved
01 Sampled
10 Enabled
11 Disabled
CC
t
EXT