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General Purpose Output (GPO) Interface

the hMc701LP6ce features a 3-wire General Purpose output (GPo) interface. GPo registers are described in

Reg1Bh table 37. the GPo is a flexible interface that supports a number of different functions and real time waveform

access including:

a. General Data output from sPi register gpo_sel_0_

data (gpo_sel=0)

b. Prescaler & reference path outputs (gpo_sel=1)

c. Lock Detect Windows (gpo_sel=2)

d. anti-cycle slip waveforms (gpo_sel=3)

e. internal synchronized frac strobe with clocks

(gposel=4)

f. Mirror of Vco serial Port Data, clock, Latch enable

(gposel=5)

g. Δ∑ Modulator Phase accumulator (gposel=6)

h. auxiliary oscillators (gposel=7)

i. auto calibration Busy flag (gposel=8)

j. Multiple Vco control, Latch enables (gposel=9)

k. Δ∑ Modulator outputs (gposel=10)

General Data to GPO (gpo_sel=0)

setting register gpo_sel=0 in table 37 assigns the 3-bit data from register gpo_sel_0_data Reg1B<6:4> to the GPo

bus.

Prescaler and Reference Path Outputs (gpo_sel = 1)

setting register gpo_sel=1 (Reg1B<3:0> table 37) results in the input crystal being buffered out to GPo3 as shown in

figure 12. this is useful for example to generate a copy of the input crystal signal to drive other circuits in the application,

while at the same time isolating the noisy circuits from the sensitive crystal output. often only the synthesizer requires

very low phase noise from the crystal, hence it is desirable to isolate other circuits from the crystal itself and allow the

synthesizer sole use of the low phase noise crystal.

gpo_sel=1 also routes the 200 Mhz 14-bit reference path divider to GP02 and the 16-bit 7 Ghz Vco path prescaler

output to GP01. this option allows the synthesizer to function as a stand alone fractional or integer prescaler and

provides visibility into the prescaler and reference path timing for sensitive applications.

Figure 12. gpo_01 Outputs

HMC701LP6CE

v05.0110

8 GHz 16-BIT FRACTIONAL-N SYNTHESIZER