Rainbow-electronics ATmega161L Manual de usuario descargar pdf (Pagina 27)

ATmega161(L)

1228C–AVR–08/02

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

tion level is nominally 1.4V (rising V

). The POR is activated whenever V

is below

the detection level. The POR circuit can be used to trigger the Start-up Reset, as well as

detect a failure in supply voltage.

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

ing the Power-on Reset threshold voltage invokes a delay counter, which determines

the delay, for which the device is kept in RESET after V

rise. The time-out period of

the delay counter can be defined by the user through the CKSEL fuses. The eight differ-

ent selections for the delay period are presented in Table 4. The RESET signal is

activated again, without any delay, when the V

decreases below detection level.

Figure 25. MCU Start-up, RESET

Tied to V

Figure 26. MCU Start-up, RESET Controlled Externally

VCC

RESET

TIME-OUT

INTERNAL

RESET

TOUT

POT

RST

VCC

RESET

TIME-OUT

INTERNAL

RESET

TOUT

POT

RST

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Rainbow-electronics ATmega161L Manual de usuario Pagina 27