Rainbow-electronics ATmega161L Manuale Utente Scaricare il pdf (Pagina 26)

ATmega161(L)

1228C–AVR–08/02

Note: 1. The Power-on Reset will not work unless the supply voltage has been below V

POT

(falling).

‘

Notes: 1. The CKSEL fuses control only the start-up time. The Oscillator is the same for all

selections. On Power-up, the real-time part of the start-up time is increased with typ.

0.6 ms.

2. External Power-on Reset.

3. Table 4 shows the Start-up Times from Reset. From sleep, only the clock counting

part of the start-up time is used. The Watchdog Oscillator is used for timing the real-

time part of the start-up time. The number WDT Oscillator cycles used for each time-

out is shown in Table 5.

The frequency of the Watchdog Oscillator is voltage-dependent as shown in the Electri-

cal Characteristics section. The device is shipped with CKSEL = 010.

Table 3. Reset Characteristics (V

=5.0V)

(1)

Symbol Parameter Min Typ Max Units

POT

Power-on Reset Threshold Voltage (rising) 1.0 1.4 1.8 V

Power-on Reset Threshold Voltage (falling)

(1)

0.4 0.6 0.8 V

RST

RESET Pin Threshold Voltage 0.85 V

Table 4. Reset Delay Selections

(3)

CKSEL

[2:0]

Start-up Time, V

=2.7V,

SUT Unprogrammed

Start-up Time, V

=4.0V,

SUT Programmed

Recommended

Usage

(1)

000 4.2 ms + 6 CK 5.8 ms + 6 CK External Clock, Fast

Rising Power

001 30 µs + 6 CK 10 µs + 6 CK External Clock

(2)

010 67 ms + 16K CK 92 ms + 16K CK Crystal Oscillator,

Slowly Rising

Power

011 4.2 ms + 16K CK 5.8 ms + 16K CK Crystal Oscillator,

Fast Rising Power

100 30 µs + 16K CK 10 µs + 16K CK Crystal Oscillator

(2)

101 67 ms + 1K CK 92 ms + 1K CK Ceramic

Resonator/External

Clock, Slowly Rising

Power

110 4.2 ms + 1K CK 5.8 ms + 1K CK Ceramic Resonator,

Fast Rising Power

111 30 µs + 1K CK 10 µs + 1K CK Ceramic

Resonator

(2)

Table 5. Number of Watchdog Oscillator Cycles

SUT Time-out Number of Cycles

Unprogrammed 4.2 ms (at V

=2.7V) 1K

Unprogrammed 67 ms (at V

= 2.7V) 16K

Programmed 5.8 ms (at V

=4.0V) 4K

Programmed 92 ms (at V

= 4.0V) 64K

1 2 ... 21 22 23 24 25 26 27 28 29 30 31 ... 158 159

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