ATMEGA169 ATMEL [ATMEL Corporation], ATMEGA169 Datasheet - Page 41

• Manufacturer Part Number: ATMEGA169
• Description: 8-bit Microcontroller with 16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Watchdog Reset
MCU Status Register –
MCUSR
2514P–AVR–07/06
When the BOD is enabled, and V
in Figure 18), the Brown-out Reset is immediately activated. When V
the trigger level (V
out period t
The BOD circuit will only detect a drop in V
for longer than t
Figure 18. Brown-out Reset During Operation
When the Watchdog times out, it will generate a short reset pulse of one CK cycle dura-
tion. On the falling edge of this pulse, the delay timer starts counting the Time-out period
t
Figure 19. Watchdog Reset During Operation
The MCU Status Register provides information on which reset source caused an MCU
reset.
• Bit 4 – JTRF: JTAG Reset Flag
This bit is set if a reset is being caused by a logic one in the JTAG Reset Register
selected by the JTAG instruction AVR_RESET. This bit is reset by a Power-on Reset, or
by writing a logic zero to the flag.
TOUT
Bit
Read/Write
Initial Value
. Refer to page 43 for details on operation of the Watchdog Timer.
CC
INTERNAL
TOUT
TIME-OUT
RESET
RESET
BOD
V
R
has expired.
7
–
0
CC
BOT+
given in Table 16.
in Figure 18), the delay counter starts the MCU after the Time-
R
6
–
0
R
5
–
0
CC
V
CK
BOT-
decreases to a value below the trigger level (V
JTRF
R/W
4
CC
if the voltage stays below the trigger level
WDRF
R/W
3
See Bit Description
BORF
R/W
V
t
2
TOUT
BOT+
ATmega169/V
EXTRF
R/W
1
CC
increases above
PORF
R/W
0
MCUSR
BOT-
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