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The board is equipped with
01
25 MHz
crystal oscillator (X4)
circuit that
provides external clock waveform
to the microcontroller
OSC1
and
OSC2
pins. This base frequency is suitable for
further clock multipliers and is also ideal for
generation of necessary USB clock, which ensures
proper operation of bootloader and your custom USB-
based applications. The board also contains
02
32.768 kHz
crystal oscillator (X5)
which provides external clock for internal
RTCC module. Microcontroller ADC requires an accurate source of
reference voltage signal. That is why we provide the external
03
voltage
reference
to the microcontroller
VREF
pin which is
2.048 V
.
5. Crystal Oscillators and 2.048 V Reference
01
02
Figure 5-1: Crystal
oscillators and 2.048 V
reference
03
01
02
03
Содержание mikromedia 5
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