AT43USB326-AU Atmel, AT43USB326-AU Datasheet - Page 39

• Manufacturer Part Number: AT43USB326-AU
• Description: IC USB KEYBOARD CTRLR 48LQFP
• Manufacturer: Atmel
• Series: AVR®r

Specifications of AT43USB326-AU

• Applications: Keyboard Controller
• Core Processor: AVR
• Program Memory Type: Mask ROM (16 kB)
• Controller Series: AT43USB
• Ram Size: 512 x 8
• Interface: USB
• Number Of I /o: 32
• Voltage - Supply: 4.4 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Watchdog Timer
3313D–USB–04/06
The Watchdog Timer is clocked from a 1 MHz clock derived from the 6 MHz on chip oscillator.
By controlling the Watchdog Timer prescaler, the Watchdog reset interval can be adjusted,
see Table 11 for a detailed description. The WDR (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 AT43USB326 resets
and executes from the reset vector.
To prevent unintentional disabling of the watchdog, a special turn-off sequence must be fol-
lowed when the watchdog is disabled. Refer to the description of the Watchdog Timer Control
Register for details.
Figure 11. Watchdog Timer
Watch Dog Timer Control Register – WDTCR
• Bits 7..5 – Res: Reserved Bits
These bits are reserved bits in the AT43USB326 and will always read as zero.
• Bit 4 – WDTOE: Watch Dog Turn-Off Enable
This bit must be set (one) when the WDE bit is cleared. Otherwise, the watchdog will not be
disabled. Once set, the 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: Watch Dog 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 procedure must be followed:
Read/Write
Initial Value
$21 ($41)
Bit
Watchdog
R
7
–
0
1 MHz Clock
Reset
R
6
–
0
R
5
–
0
WDP0
WDP1
WDP2
WDE
WDTOE
R/W
4
0
WDE
R/W
3
0
Watchdog Prescaler
WDP2
R/W
MCU Reset
2
0
WDP1
AT43USB326
R/W
1
0
WDP0
R/W
0
0
WDTCR
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