AT90USB162 Atmel Corporation, AT90USB162 Datasheet - Page 53

• Manufacturer Part Number: AT90USB162
• Manufacturer: Atmel Corporation

Specifications of AT90USB162

• Flash (kbytes): 16 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 22
• Ext Interrupts: 21
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 2
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 0.5
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 5
• Input Capture Channels: 1
• Pwm Channels: 4
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

7707F–AVR–11/10
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Figure 9-8.
The Watchdog Timer (WDT) is a timer counting cycles of a separate on-chip 128 kHz oscillator.
The WDT gives a early warning interrupt when the counter reaches a given time-out value. The
WDT gives an interrupt or a system reset when the counter reaches two times the given time-out
value. In normal operation mode, it is required that the system uses the WDR - Watchdog Timer
Reset - instruction to restart the counter before the time-out value is reached. If the system
doesn't restart the counter, an interrupt or system reset will be issued.
In Interrupt mode, the WDT gives an interrupt when the timer expires two times. This interrupt
can be used to wake the device from sleep-modes, and also as a general system timer. One
example is to limit the maximum time allowed for certain operations, giving an interrupt when the
operation has run longer than expected.
In System Reset mode, the WDT gives a reset when the timer expires two times. This is typically
used to prevent system hang-up in case of runaway code.
The third mode, Interrupt and System Reset mode, combines the other two modes by first giving
an interrupt and then switch to System Reset mode. This mode will for instance allow a safe
shutdown by saving critical parameters before a system reset.
In addition to these modes, the early warning interrupt can be enabled in order to generate an
interrupt when the WDT counter expires the first time.
The Watchdog always on (WDTON) fuse, if programmed, will force the Watchdog Timer to Sys-
tem Reset mode. With the fuse programmed the System Reset mode bit (WDE) and Interrupt
mode bit (WDIE) are locked to 1 and 0 respectively. To further ensure program security, altera-
tions to the Watchdog set-up must follow timed sequences. The sequence for clearing WDE or
changing time-out configuration is as follows:
Selectable Time-out period from 16ms to 8s
Possible Hardware fuse Watchdog always on (WDTON) for fail-safe mode
Early warning after one Time-Out period reached, programmable Reset (see operating modes)
after 2 Time-Out periods reached.
Watchdog Timer
OSCILLATOR
CLOCK
DIVIDER
128kHz
WATCHDOG
RESET
OSC/1
OSC/3
OSC/5
OSC/7
WDEWIE
WDIE
WDIF
WDE
AT90USB82/162
WDP0
WDP1
WDP2
WDP3
MCU RESET
INTERRUPT
EARLY WARNING
INTERRUPT
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