AT90S1200 Ver la hoja de datos (PDF) - Atmel Corporation

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AT90S1200

8-Bit Microcontroller with 1K bytes In-System Programmable Flash

Atmel Corporation 

External Reset

Watchdog Reset

been applied, the Power-on Reset period can be extended. Refer to Figure 15 for a tim-

ing example on this.

Figure 15. MCU Start-up, RESET Controlled Externally

VCC

VPOT

RESET

VRST

TIME-OUT

tTOUT

INTERNAL

RESET

An External Reset is generated by a low level on the RESET pin. Reset pulses longer

than 50 ns will generate a reset, even if the clock is not running. Shorter pulses are not

guaranteed to generate a reset. When the applied signal reaches the Reset Threshold

Voltage (VRST) on its positive edge, the delay timer starts the MCU after the Time-out

period tTOUT has expired.

Figure 16. External Reset during Operation

VCC

RESET

TIME-OUT

INTERNAL

RESET

When the Watchdog times out, it will generate a short reset pulse of 1 XTAL cycle dura-

tion. On the falling edge of this pulse, the delay timer starts counting the Time-out period

tTOUT. Refer to page 23 for details on operation of the Watchdog.

14 AT90S1200

0838H–AVR–03/02

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