Atmel Evaluation-Board AT90USBKey AT90USBKey AT90USBKey-2 データシート
製品コード
AT90USBKey-2
Using the AT90USBKey
2-8
AT90USBKey Hardware User Guide
7627A–AVR–04/06
2.3
Reset
Although the AT90USB has its on-chip RESET circuitry (c.f. AT90USB Datasheet,
section “System Control and Reset), the AVRUSBKey provides to the AT90USB a
RESET signal witch can come from two different sources:
section “System Control and Reset), the AVRUSBKey provides to the AT90USB a
RESET signal witch can come from two different sources:
Figure 2-4 . Reset Implementation
2.3.1
Power-on RESET
The on-board RC network acts as power-on RESET.
2.3.2
RESET Push Button
By pressing the RESET push button on the AVRUSBKey, a warm RESET of the
AT90USB is performed.
AT90USB is performed.
2.3.3
Main Clock XTAL
To use the USB interface of the AT90USB, the clock source should always be a crystal
or external clock oscillator (the internal 8MHz RC oscillator can not be used to operate
with the USB interface). Only the following crystal frequency allows proper USB
operations: 2MHz, 4MHz, 6MHz, 8MHz, 12MHz, 16MHz. The AT90USBKey comes with
a default 8MHz crystal oscillator.
or external clock oscillator (the internal 8MHz RC oscillator can not be used to operate
with the USB interface). Only the following crystal frequency allows proper USB
operations: 2MHz, 4MHz, 6MHz, 8MHz, 12MHz, 16MHz. The AT90USBKey comes with
a default 8MHz crystal oscillator.
RST
VCC
R6
47k
47k
C8
220nF
RESET