AT90PWM2(2005) View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

AT90PWM2
(Rev.:2005)

8-bit Microcontroller with 8K Bytes In-System Programmable Flash

Atmel Corporation 

Watchdog Reset

When the BOD is enabled, and VCC decreases to a value below the trigger level (VBOT-

in Figure 21), the Brown-out Reset is immediately activated. When VCC increases above

the trigger level (VBOT+ in Figure 21), the delay counter starts the MCU after the Time-

out period tTOUT has expired.

The BOD circuit will only detect a drop in VCC if the voltage stays below the trigger level

for longer than tBOD given in Table 16.

Figure 21. Brown-out Reset During Operation

VCC

VBOT-

VBOT+

RESET

TIME-OUT

tTOUT

INTERNAL

RESET

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

tTOUT. Refer to page 50 for details on operation of the Watchdog Timer.

Figure 22. Watchdog Reset During Operation

CC

CK

MCU Status Register –

MCUSR

The MCU Status Register provides information on which reset source caused an MCU

reset.

Bit

7

6

5

4

3

2

1

0

–

–

–

–

WDRF BORF EXTRF PORF MCUSR

Read/Write

R

R

R

R

R/W

R/W

R/W

R/W

Initial Value

0

0

0

0

See Bit Description

• Bit 3 – WDRF: 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.

48 AT90PWM2/3

4317B–AVR–02/05

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