DOC7707 datasheet(56/307 Pages) ETC1

56 / 307 page

7707F–AVR–11/10

AT90USB82/162

The following code example shows one assembly and one C function for changing the time-out

value of the Watchdog Timer.

Note:

1. The example code assumes that the part specific header file is included.

Note: The Watchdog Timer should be reset before any change of the WDP bits, since a change

in the WDP bits can result in a time-out when switching to a shorter time-out period.

9.9.1

Watchdog Timer Control Register - WDTCSR

• Bit 7 - WDIF: Watchdog Interrupt Flag

This bit is set when a time-out occurs twice in the Watchdog Timer and if the Watchdog Timer is

configured for interrupt. WDIF is automatically cleared by hardware when executing the corre-

Assembly Code Example(1)

WDT_Prescaler_Change:

; Turn off global interrupt

cli

; Reset Watchdog Timer

wdr

; Start timed sequence

r16, WDTCSR

ori

r16, (1<<WDCE) | (1<<WDE)

out

WDTCSR, r16

; --

Got four cycles to set the new values from here -

; Set new prescaler(time-out) value = 64K cycles (~0.5 s)

ldi

r16, (1<<WDE) | (1<<WDP2) | (1<<WDP0)

out

WDTCSR, r16

; --

Finished setting new values, used 2 cycles -

; Turn on global interrupt

sei

ret

C Code Example

(1)

void WDT_Prescaler_Change(void)

{

__disable_interrupt();

__watchdog_reset();

/* Start timed

equence */

WDTCSR |= (1<<WDCE) | (1<<WDE);

/* Set new prescaler(time-out) value = 64K cycles (~0.5 s) */

WDTCSR

= (1<<WDE) | (1<<WDP2) | (1<<WDP0);

__enable_interrupt();

}

Bit

7654

WDIF

WDIE

WDP3

WDCE

WDE

WDP2

WDP1

WDP0

WDTCSR

Read/Write

R/WR/W

Initial Value

0000

DOC7707 Datasheet(PDF) 56 Page - List of Unclassifed Manufacturers

DOC7707 Datasheet(HTML) 56 Page - List of Unclassifed Manufacturers

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL