ATmega48 datasheet(42/340 Pages) ATMEL

42 / 340 page

7530H–AVR–02/09

ATmega48/88/168 Automotive

8.0.2

Reset Sources

The ATmega48/88/168 has four sources of reset:

• Power-on Reset. The MCU is reset when the supply voltage is below the Power-on Reset

threshold (V

POT).

• External Reset. The MCU is reset when a low level is present on the RESET pin for longer

than the minimum pulse length.

• Watchdog System Reset. The MCU is reset when the Watchdog Timer period expires and

the Watchdog System Reset mode is enabled.

• Brown-out Reset. The MCU is reset when the supply voltage V

CC is below the Brown-out

Reset threshold (V

BOT) and the Brown-out Detector is enabled.

Figure 8-1.

Reset Logic

8.0.3

Power-on Reset

A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The detection level

is defined in Table 8-1 on page 43. The POR is activated whenever V

CC is below the detection

level. The POR circuit can be used to trigger the start-up Reset, as well as to detect a failure in

supply voltage.

A Power-on Reset (POR) circuit ensures that the device is reset from Power-on. Reaching the

Power-on Reset threshold voltage invokes the delay counter, which determines how long the

device is kept in RESET after V

CC rise. The RESET signal is activated again, without any delay,

when V

CC decreases below the detection level.

MCU Status

Brown-out

Reset Circuit

BODLEVEL [2..0]

Delay Counters

CKSEL[3:0]

TIMEOUT

DATA BUS

Clock

Generator

SPIKE

FILTER

Pull-up Resistor

Watchdog

Oscillator

SUT[1:0]

Power-on Reset

Circuit

RSTDISBL

ATmega48 Datasheet(PDF) 42 Page - ATMEL Corporation

ATmega48 Datasheet(HTML) 42 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Descarga

Enlace URL