In the datasheet of 555 timer, the reset pin can take voltage upto 1v(max.) to reset.
Then why the reset pin is connected to Vcc(12V) for Astable multivibrator mode????
Correction: The 555 will reset if its Reset pin voltage is 0V to 1V. The reset pin is normally connected to the positive power supply voltage to prevent resetting.
To avoid reset it is connected to VCC. You can even connect it to VCC through a reset switch (one end to VCC and another to ground through a resistor) to make it reset. But the voltage has to fall below 1V to make the IC to reset.
Correction: The 555 will reset if its Reset pin voltage is 0V to 1V. The reset pin is normally connected to the positive power supply voltage to prevent resetting.