ATTINY25-20SSNR Atmel, ATTINY25-20SSNR Datasheet - Page 45
![IC MCU AVR 2KB FLASH 20MHZ 8SOIC](/photos/18/29/182913/8-soic_sml.jpg)
ATTINY25-20SSNR
Manufacturer Part Number
ATTINY25-20SSNR
Description
IC MCU AVR 2KB FLASH 20MHZ 8SOIC
Manufacturer
Atmel
Series
AVR® ATtinyr
Specifications of ATTINY25-20SSNR
Core Processor
AVR
Core Size
8-Bit
Speed
20MHz
Connectivity
USI
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
6
Program Memory Size
2KB (1K x 16)
Program Memory Type
FLASH
Eeprom Size
128 x 8
Ram Size
128 x 8
Voltage - Supply (vcc/vdd)
2.7 V ~ 5.5 V
Data Converters
A/D 4x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
8-SOIC (0.154", 3.90mm Width)
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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8.4.1
8.4.1.1
8.4.1.2
2586M–AVR–07/10
Timed Sequences for Changing the Configuration of the Watchdog Timer
Safety Level 1
Safety Level 2
“Timed Sequences for Changing the Configuration of the Watchdog Timer” on page 45
details.
Table 8-1.
Figure 8-7.
The sequence for changing configuration differs slightly between the two safety levels. Separate
procedures are described for each level.
In this mode, the Watchdog Timer is initially disabled, but can be enabled by writing the WDE bit
to one without any restriction. A timed sequence is needed when disabling an enabled Watch-
dog Timer. To disable an enabled Watchdog Timer, the following procedure must be followed:
In this mode, the Watchdog Timer is always enabled, and the WDE bit will always read as one. A
timed sequence is needed when changing the Watchdog Time-out period. To change the
Watchdog Time-out, the following procedure must be followed:
WDTON
Unprogrammed
Programmed
1. In the same operation, write a logic one to WDCE and WDE. A logic one must be writ-
2. Within the next four clock cycles, in the same operation, write the WDE and WDP bits
1. In the same operation, write a logical one to WDCE and WDE. Even though the WDE
2. Within the next four clock cycles, in the same operation, write the WDP bits as desired,
ten to WDE regardless of the previous value of the WDE bit.
as desired, but with the WDCE bit cleared.
always is set, the WDE must be written to one to start the timed sequence.
but with the WDCE bit cleared. The value written to the WDE bit is irrelevant.
WDT Configuration as a Function of the Fuse Settings of WDTON
Watchdog Timer
Safety
Level
1
2
WATCHDOG
OSCILLATOR
RESET
128 kHz
WDP0
WDP1
WDP2
WDP3
WDE
WDT Initial
State
Disabled
Enabled
How to Disable the
WDT
Timed sequence
Always enabled
MCU RESET
PRESCALER
WATCHDOG
How to Change Time-
out
No limitations
Timed sequence
for
45
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