AT43USB325 datasheet(53/109 Pages) ATMEL

53 / 109 page

3355C–USB–4/05

AT43USB325

down-counting compare match is not interpreted to be reached before the next time the counter

reaches the TOP value, making a one-period PWM pulse.

Note:

X = A or B

In PWM mode, the Timer Overflow Flag1, TOV1, is set when the counter advances from $0000.

Timer Overflow Interrupt1 operates exactly as in normal Timer/Counter mode, i.e. it is executed

when TOV1 is set provided that Timer Overflow Interrupt1 and global interrupts are enabled.

This also applies to the Timer Output Compare1 flags and interrupts.

6.5

Watchdog Timer

The Watchdog Timer is clocked from a 1 MHz clock derived from the 6 MHz on chip oscillator.

By controlling the Watchdog Timer prescaler, the Watchdog reset interval can be adjusted, see

Table 6-8 for a detailed description. The WDR (Watchdog Reset) instruction resets the Watch-

dog Timer. Eight different clock cycle periods can be selected to determine the reset period. If

the reset period expires without another Watchdog reset, the AT43USB325 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. Refer to the description of the Watchdog Timer Control Register

for details.

Figure 6-6.

Watchdog Timer

Table 6-7.

PWM Outputs OCR1X = $0000 or Top

COM1X1

COM1X0

OCR1X

Output OC1X

$0000

TOP

$0000

TOP

1 MHz Clock

MCU Reset

WDE

WDP2

WDP1

WDP0

Watchdog

Reset

Watchdog Prescaler

AT43USB325 Datasheet(PDF) 53 Page - ATMEL Corporation

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