ATTIny2313-16MI ATMEL Corporation, ATTIny2313-16MI Datasheet - Page 38

• Manufacturer Part Number: ATTIny2313-16MI
• Description: 8-bit AVR Microcontroller with 2K Bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

Internal Voltage
Reference
Voltage Reference Enable
Signals and Start-up Time
Watchdog Timer
38
ATtiny2313/V
ATtiny2313 features an internal bandgap reference. This reference is used for Brown-
out Detection, and it can be used as an input to the Analog Comparator.
The voltage reference has a start-up time that may influence the way it should be used.
The start-up time is given in Table 18. To save power, the reference is not always turned
on. The reference is on during the following situations:
1. When the BOD is enabled (by programming the BODLEVEL [2..0] Fuse).
2. When the bandgap reference is connected to the Analog Comparator (by setting
Thus, when the BOD is not enabled, after setting the ACBG bit, the user must always
allow the reference to start up before the output from the Analog Comparator is used. To
reduce power consumption in Power-down mode, the user can avoid the three condi-
tions above to ensure that the reference is turned off before entering Power-down mode.
Table 18. Internal Voltage Reference Characteristics
Note:
The Watchdog Timer is clocked from an On-chip Oscillator which runs at 128 kHz. By
controlling the Watchdog Timer prescaler, the Watchdog Reset interval can be adjusted
as shown in Table 21 on page 41. The WDR – Watchdog Reset – instruction resets the
Watchdog Timer value to 0. The Watchdog Timer is also reset when it is disabled and
when a Chip Reset occurs. Ten different clock cycle periods can be selected to deter-
mine the reset period. If the reset period expires without another Watchdog Reset, the
ATtiny2313 resets and executes from the Reset Vector. For timing details on the Watch-
dog Reset, refer to Table 21 on page 41.
The Watchdog Timer can also be configured to generate an interrupt instead of a reset.
This can be very helpful when using the Watchdog to wake-up from Power-down.
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
19. Refer to “Timed Sequences for Changing the Configuration of the Watchdog Timer”
on page 43 for details.
Table 19. WDT Configuration as a Function of the Fuse Settings of WDTON
Symbol
WDTON
Unprogrammed
Programmed
V
t
I
the ACBG bit in ACSR).
BG
BG
BG
1. Values are guidelines only. Actual values are TBD.
Parameter
Bandgap reference voltage
Bandgap reference start-up time
Bandgap reference current
consumption
Safety
Level
1
2
WDT Initial
State
Disabled
Enabled
How to Disable the
WDT
Timed sequence
Always enabled
V
V
V
Condition
T
T
T
CC
CC
CC
A
A
A
= 25°C
= 25°C
= 25°C
= 2.7V,
= 2.7V,
= 2.7V,
(1)
Min
1.0
Typ
How to Change
Time-out
No limitations
Timed sequence
1.1
40
15
2543C–AVR–12/03
Max
1.2
70
Units
µA
µs
V