IP2022 Data Sheet www.ubicom.com 25 3.7.1 External Connections Figure 3-17 shows the connections for driving the OSC or
RTCLK clock sources with an external signal. To drive the
OSC clock source, the external clock signal is driven on
the OSC1 pin and the OSC2 pin is left open. The external
clock   signal   driven   on   the   OSC1   pin   may   be   any
frequency  up  to  150  MHz.  To  drive  the  RTCLK  clock
source, the external clock signal is driven on the RTCLK1
input and the RTCLK2 output is left open. The external
clock  signal  driven  on  the  RTCLK1  pin  may  be  any
frequency up to 100 MHz. Figure 3-17  External Clock Input Figure   3-18   shows   the   connections   for   attaching   an
external crystal to the OSC or RTCLK oscillator. For the
OSC oscillator, a crystal between 1 MHz and 6 MHz is
connected  across  the  OSC1  and  OSC2  pins.  For  the
RTCLK  oscillator,  a  32.768  kHz  crystal  is  connected
across   the   RTCLK1   and   RTCLK2   pins.   No   external
capacitors are required. For proper operation of the crystal or resonator, the total
printed circuit board trace length for the OSC1 and OSC2
signals must be kept to less than 1 inch (2.5 cm) each,
and  the  capacitive  loading  must  be  kept  to  less  than  3
picofarads. Routing should be direct and no vias should
be used. Figure 3-18  Crystal Connection Figure   3-19   shows   the   connections   for   attaching   an
external  ceramic  resonator  to  the  OSC  oscillator.  The
frequency of the resonator must be between 1 MHz and 6
MHz. The value of the external capacitors C1 and C2 is 5
pF.  The  RTCLK  oscillator  may  not  be  used  with  an
external ceramic resonator. Figure 3-19  Ceramic Resonator Connection RTCLK1   RTCLK2       Externally
Generated Clock Open 515-024.eps IP2022 OSC1 OSC2       Externally
Generated Clock Open 515-025.eps Crystal Crystal IP2022 OSC1 OSC2 XTAL RTCLK1 RTCLK2 RTCLK C1 515-039.eps C2   Ceramic
Resonator IP2022 OSC1 OSC2 XTAL