ATMEGA168PA-PU Atmel, ATMEGA168PA-PU Datasheet - Page 56

MCU, 8BIT, AVR, 16K FLASH, 28PDIP

ATMEGA168PA-PU

Manufacturer Part Number
ATMEGA168PA-PU
Description
MCU, 8BIT, AVR, 16K FLASH, 28PDIP
Manufacturer
Atmel
Datasheet

Specifications of ATMEGA168PA-PU

Controller Family/series
Atmega
No. Of I/o's
23
Eeprom Memory Size
512Byte
Ram Memory Size
1KB
Cpu Speed
20MHz
No.
RoHS Compliant
Core Size
8bit
Program Memory Size
16KB
Oscillator Type
External, Internal
Rohs Compliant
Yes

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
ATMEGA168PA-PU
Manufacturer:
TI
Quantity:
1 240
8271C–AVR–08/10
Watchdog Timer will set WDIF. Executing the corresponding interrupt vector will clear WDIE and
WDIF automatically by hardware (the Watchdog goes to System Reset Mode). This is useful for
keeping the Watchdog Timer security while using the interrupt. To stay in Interrupt and System
Reset Mode, WDIE must be set after each interrupt. This should however not be done within the
interrupt service routine itself, as this might compromise the safety-function of the Watchdog
System Reset mode. If the interrupt is not executed before the next time-out, a System Reset
will be applied.
Table 10-1.
Note:
• Bit 4 – WDCE: Watchdog Change Enable
This bit is used in timed sequences for changing WDE and prescaler bits. To clear the WDE bit,
and/or change the prescaler bits, WDCE must be set.
Once written to one, hardware will clear WDCE after four clock cycles.
• Bit 3 – WDE: Watchdog System Reset Enable
WDE is overridden by WDRF in MCUSR. This means that WDE is always set when WDRF is
set. To clear WDE, WDRF must be cleared first. This feature ensures multiple resets during con-
ditions causing failure, and a safe start-up after the failure.
• Bit 5, 2:0 - WDP[3:0]: Watchdog Timer Prescaler 3, 2, 1 and 0
The WDP[3:0] bits determine the Watchdog Timer prescaling when the Watchdog Timer is run-
ning. The different prescaling values and their corresponding time-out periods are shown in
Table 10-2 on page
Table 10-2.
ATmega48A/48PA/88A/88PA/168A/168PA/328/328
WDTON
WDP3
0
0
0
0
0
0
0
1
1
1
1
0
1. WDTON Fuse set to “0” means programmed and “1” means unprogrammed.
(1)
WDP2
0
0
0
0
1
1
1
Watchdog Timer Configuration
Watchdog Timer Prescale Select
WDE
0
0
1
1
x
56.
WDP1
0
0
1
1
0
0
1
WDIE
WDP0
0
1
0
1
x
0
1
0
1
0
1
0
Mode
Stopped
Interrupt Mode
System Reset Mode
Interrupt and System Reset
Mode
System Reset Mode
Number of WDT Oscillator
128K (131072) cycles
16K (16384) cycles
32K (32768) cycles
64K (65536) cycles
2K (2048) cycles
4K (4096) cycles
8K (8192) cycles
Cycles
Action on Time-out
None
Interrupt
Reset
Interrupt, then go to System
Reset Mode
Reset
Typical Time-out at
V
CC
0.125 s
16 ms
32 ms
64 ms
0.25 s
0.5 s
1.0 s
= 5.0V
56

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