Rainbow-electronics Atmega169L Manuel d'utilisateur télécharger pdf (Page 40)

ATmega169V/L

2514A–AVR–08/02

When the BOD is enabled, and V

decreases to a value below the trigger level (V

BOT-

in Figure 18), the Brown-out Reset is immediately activated. When V

increases above

the trigger level (V

BOT+

in Figure 18), the delay counter starts the MCU after the Time-

out period t

TOUT

has expired.

The BOD circuit will only detect a drop in V

if the voltage stays below the trigger level

for longer than t

BOD

given in Table 16.

Figure 18. Brown-out Reset During Operation

Watchdog 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

TOUT

. Refer to page 42 for details on operation of the Watchdog Timer.

Figure 19. Watchdog Reset During Operation

MCU Status Register –

MCUSR

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.

RESET

TIME-OUT

INTERNAL

RESET

BOT-

BOT+

TOUT

Bit 76543210

– – – JTRF WDRF BORF EXTRF PORF MCUSR

Read/Write R R R R/W R/W R/W R/W R/W

Initial Value 0 0 0 See Bit Description

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 316 317

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Rainbow-electronics Atmega169L Manuel d'utilisateur Page 40

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