XC2200 Derivatives
System Units (Vol. 1 of 2)
System Control Unit (SCU)
User’s Manual
6-4
V2.1, 2008-08
SCU, V1.13
6.1.2
Trimmed Current Controlled Wake-up Clock (OSC_WU)
The trimmed current controlled wake-up clock source provides a clock to control internal
operations independent of the standard clock supplies and requires no external
components. Its output frequency
f
WU
is configured via bit field WUOSCCON.FREQSEL
and has a typical range from 130 kHz to 500 kHz.
6.1.3
High Precision Oscillator Circuit (OSC_HP)
The high precision oscillator circuit can drive an external crystal or accepts an external
clock source. It consists of an inverting amplifier with XTAL1 as input, and XTAL2 as
output.
and
show the recommended external circuitries for both
operating modes, External Crystal Mode and External Input Clock Mode.
6.1.3.1
External Input Clock Mode
An external clock signal is supplied directly not using an external crystal and bypassing
the amplifier of the oscillator. The maximum allowed input frequency depends on the
characteristics of pin XTAL1.
When using an external clock signal it must be connected to XTAL1. XTAL2 is left open
(unconnected).
Note: XTAL1 belongs to core voltage domain DMP_1 and, therefore, accepts only a
reduced voltage range. Voltages on XTAL1 must comply to the voltage defined in
the data sheet.
Figure 6-3
XC2200 External Clock Input Mode for the High-Precision Oscillator
CGU_OSC_HP_ExtIn.vsd
OSC_HP
f
OSC
XTAL1
XTAL2
VSS
External
Clock Signal
leave unconnected