Answer to Question #159340 in Assembler for Raya

Question

Write about Oscillator and watchdog timer in ATmega32 microcontroller..

Answer 1

XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can be configured for use as an On-chip Oscillator. Either a quartz crystal or a ceramic resonator may be used. The CKOPT Fuse selects between two different Oscillator amplifier modes. When CKOPT is programmed, the Oscillator output will oscillate will a full railto-rail swing on the output. This mode is suitable when operating in a very noisy environment or when the output from XTAL2 drives a second clock buffer. This mode has a wide frequency range. When CKOPT is unprogrammed, the Oscillator has a smaller output swing. This reduces power consumption considerably. This mode has a limited frequency range and it can not be used to drive other clock buffers.  

The Watchdog Timer is clocked from a separate On-chip Oscillator which runs at 1MHz. This is the typical value at VCC = 5V. By controlling the Watchdog Timer prescaler, the Watchdog Reset interval can be adjusted. The WDR – Watchdog Reset – instruction resets the Watchdog Timer. The Watchdog Timer is also reset when it is disabled and when a Chip Reset occurs. Eight different clock cycle periods can be selected to determine the reset period. If the reset period expires without another Watchdog Reset, the ATmega32 resets and executes from the Reset Vector. To prevent unintentional disabling of the Watchdog, a special turn-off sequence must be followed when the Watchdog is disabled.