ATTINY28V-1AC Atmel, ATTINY28V-1AC Datasheet - Page 37

• Manufacturer Part Number: ATTINY28V-1AC
• Description: IC AVR MCU 2K 1.2MHZ 1.8V 32TQFP
• Manufacturer: Atmel
• Series: AVR® ATtinyr

Specifications of ATTINY28V-1AC

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 1.2MHz
• Peripherals: POR, WDT
• Number Of I /o: 11
• Program Memory Size: 2KB (1K x 16)
• Program Memory Type: FLASH
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 32-TQFP, 32-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Ram Size: -
• Data Converters: -
• Connectivity: -

Watchdog Timer
Register Description
Watchdog Timer Control
Register – WDTCR
1062F–AVR–07/06
The Watchdog Timer is clocked from a separate on-chip oscillator. By controlling the
Watchdog Timer prescaler, the Watchdog reset interval can be adjusted as shown in
Table 15. See characterization data for typical values at other V
(Watchdog Reset) instruction resets the Watchdog Timer. Eight different clock cycle
periods can be selected to determine the reset period. If the reset period expires without
another Watchdog reset, the ATtiny28 resets and executes from the reset vector. For
timing details on the Watchdog reset, refer to page 18.
To prevent unintentional disabling of the Watchdog, a special turn-off sequence must be
followed when the Watchdog is disabled. Refer to the description of the Watchdog Timer
Control Register for details.
Figure 30. Watchdog Timer
• Bits 7..5 - Res: Reserved Bits
These bits are reserved bits in the ATtiny28 and will always read as zero.
• Bit 4 – WDTOE: Watchdog Turn-off Enable
This bit must be set (one) when the WDE bit is cleared. Otherwise, the Watchdog will
not be disabled. Once set, hardware will clear this bit to zero after four clock cycles.
Refer to the description of the WDE bit for a Watchdog disable procedure.
• Bit 3 – WDE: Watchdog Enable
When the WDE is set (one), the Watchdog Timer is enabled and if the WDE is cleared
(zero), the Watchdog Timer function is disabled. WDE can only be cleared if the
WDTOE bit is set (one). To disable an enabled Watchdog Timer, the following proce-
dure must be followed:
Bit
$01
Read/Write
Initial Value
R
7
–
0
Oscillator
350 kHz at V
110 kHz at V
1 MHz at V
R
6
–
0
CC
CC
CC
= 5V
= 3V
= 2V
R
5
–
0
WDTOE
R/W
4
0
WDE
R/W
3
0
WDP2
R/W
2
0
WDP1
ATtiny28L/V
R/W
1
0
CC
levels. The WDR
WDP0
R/W
0
0
WDTCR
37