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Hardware Preparation and Installation
MC92602 Reduced Interface SerDes Design Verification Board User’s Guide, Rev. 3
2-4
Freescale Semiconductor
2.4.1
Using the Onboard Oscillator
There are two available positions for using onboard oscillators. A standard 14-pin DIP socket is available
on the board to allow the user to easily change frequencies by swapping in crystal oscillators with other
values. The onboard oscillators must be two times (2
×
) the desired MVC92602 reference clock frequency.
The default reference clock frequency oscillator supplied with the board is 250 MHz.
Crystal oscillators used with this board should have +3.3-V complementary PECL outputs capable of
driving a line terminated with 50
Ω
. Oscillators conforming to these specifications are also available in
J-lead SMT packages and can be soldered onto the underside of the MC92602DVB at location Y2. This
oscillator, Y2, can then be enabled by placing SW1 switch 1 in the ‘off’ position. Both types of crystal
oscillators are available from external vendors in a variety of frequencies. Once either type of oscillator is
installed, SW1 switch 2 must be placed in the ‘on’ position to select the onboard oscillator.
2.4.2
External Reference Clock Source
The input reference clock can also be supplied by using an external reference clock into the clock buffer
circuit on the board via the CLK_IN SMA connector. To supply an external reference clock, switch
number 2 on SW1 must be set to the ‘off’ position. The user must then supply a 1.0-Vp-p input clock via
the SMA connector. The CLK_IN input is AC coupled on the board and, therefore, does not require any
DC biasing of the input signal. This external clock input is also terminated with a 50-
Ω
impedance.
2.4.3
Supplying a Clock to the MC92602
The input reference clock, from either the onboard oscillator or an external source, is applied to a
MC100ES6222 clock buffer. This buffer has an input clock select multiplexer, and a programmable
divide-by-one/divide-by-two function. The buffer also contains a master reset (Enable). It is recommended
that this reset, found on SW1 switch 4, be activated, then deactivated after changing the divide-by-
xx
switch. This will ensure proper frequency generation.
Between the MC100ES6222 output and the MC92602 reference clock inputs, REF_CLK_P and
REF_CLK_N, is an MC100ES8111 which performs a PECL to HSTL level shift. It also drives two SMA
connectors, 1.5V_CLK_OUT5 and 1.5V_CLK_OUT6, with HSTL level clock signals.
NOTE
The outputs of the MCP100ES8111 expect to see a DC 50-
Ω
path to ground.
Therefore, if a DC blocker is being used with the 1.5V_CLK_OUT5 or
1.5V_CLK_OUT6 outputs as a trigger or signal to an oscilloscope, a 50-
Ω
feed through termination must be placed in line before the DC blocker and
before the attachment to the oscilloscope. A 3dB attenuator may be used in
place of the 50-
Ω
feed through termination.
Содержание MC92602
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