57
7679H–CAN–08/08
AT90CAN32/64/128
ADC is used. To reduce power consumption in Power-down mode, the user can avoid the three
conditions above to ensure that the reference is turned off before entering Power-down mode.
7.2.2
Voltage Reference Characteristics
7.3
Watchdog Timer
The Watchdog Timer is clocked from a separate On-chip Oscillator which runs at 1 MHz. This is
the typical value at V
CC
= 5V. See characterization data for typical values at other V
CC
levels. By
controlling the Watchdog Timer prescaler, the Watchdog Reset interval can be adjusted as
shown in
. 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 AT90CAN32/64/128 resets and executes
from the Reset Vector. For timing details on the Watchdog Reset, refer to
To prevent unintentional disabling of the Watchdog or unintentional change of time-out period,
two different safety levels are selected by the fuse WDTON as shown in Table 7-5. Refer to
“Timed Sequences for Changing the Configuration of the Watchdog Timer” on page 59
details.
Figure 7-7.
Watchdog Timer
Table 7-4.
Internal Voltage Reference Characteristics
Symbol
Parameter
Condition
Min.
Typ.
Max.
Units
V
BG
Bandgap reference voltage
1.0
1.1
1.2
V
t
BG
Bandgap reference start-up time
40
70
µs
I
BG
Bandgap reference current
consumption
15
µA
Table 7-5.
WDT Configuration as a Function of the Fuse Settings of WDTON
WDTON
Safety
Level
WDT Initial
State
How to Disable
the WDT
How to Change
Time-out
Unprogrammed
1
Disabled
Timed sequence
Timed sequence
Programmed
2
Enabled
Always enabled
Timed sequence
WATCHDOG
OSCILLATOR
~1 MHz
Содержание AVR AT90CAN128
Страница 414: ...414 7679H CAN 08 08 AT90CAN32 64 128 32 2 QFN64...
Страница 415: ...415 7679H CAN 08 08 AT90CAN32 64 128...