ATMEGA3250PV-10AUR Atmel, ATMEGA3250PV-10AUR Datasheet - Page 51

• Manufacturer Part Number: ATMEGA3250PV-10AUR
• Description: MCU AVR 32K FLASH 10MHZ 100TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA3250PV-10AUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 10MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 69
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

10.5.2
8023F–AVR–07/09
WDTCR – Watchdog Timer Control Register
• Bits 7:5 – Res: Reserved Bits
These bits are reserved and will always read as zero.
• Bit 4 – WDCE: Watchdog Change Enable
This bit must be set when the WDE bit is written to logic zero. Otherwise, the Watchdog will not
be disabled. Once written to one, hardware will clear this bit after four clock cycles. Refer to the
description of the WDE bit for a Watchdog disable procedure. This bit must also be set when
changing the prescaler bits. See
Watchdog Timer” on page
• Bit 3 – WDE: Watchdog Enable
When the WDE is written to logic one, the Watchdog Timer is enabled, and if the WDE is written
to logic zero, the Watchdog Timer function is disabled. WDE can only be cleared if the WDCE bit
has logic level one. To disable an enabled Watchdog Timer, the following procedure must be
followed:
1. In the same operation, write a logic one to WDCE and WDE. A logic one must be written
2. Within the next four clock cycles, write a logic 0 to WDE. This disables the Watchdog.
In safety level 2, it is not possible to disable the Watchdog Timer, even with the algorithm
described above.
• Bits 2:0 – WDP2, WDP1, WDP0: Watchdog Timer Prescaler 2, 1, and 0
The WDP2, WDP1, and WDP0 bits determine the Watchdog Timer prescaling when the Watch-
dog Timer is enabled. The different prescaling values and their corresponding Time-out Periods
are shown in
Table 10-2.
Bit
(0x60)
Read/Write
Initial Value
WDP2
to WDE even though it is set to one before the disable operation starts.
0
0
0
0
1
1
1
1
WDP1
Table 10-2 on page
0
0
1
1
0
0
1
1
Watchdog Timer Prescale Select
R
7
–
0
See Section “10.4.1” on page 49.
WDP0
0
1
0
1
0
1
0
1
R
6
–
0
49.
Oscillator Cycles
Number of WDT
51.
1,024K cycles
2,048K cycles
128K cycles
256K cycles
512K cycles
R
”Timed Sequences for Changing the Configuration of the
16K cycles
32K cycles
64K cycles
5
–
0
WDCE
R/W
4
0
WDE
R/W
3
0
Typical Time-out at
ATmega325P/3250P
V
CC
17.1 ms
34.3 ms
68.5 ms
0.14 s
0.27 s
0.55 s
WDP2
1.1 s
2.2 s
R/W
= 3.0V
2
0
WDP1
R/W
1
0
Typical Time-out at
WDP0
R/W
V
0
0
CC
16.3 ms
32.5 ms
65 ms
0.13 s
0.26 s
0.52 s
1.0 s
2.1 s
= 5.0V
WDTCR
51