Symmetricom ET6000, Руководство пользователя

Страница: 12 / 206

GENERAL INFORMATION
A. J4 - TRACKING
This CMOS output level is “low” when the unit is actively acquiring data from
satellites. In the Stationary Mode, the unit has to track at least one satellite for the
Tracking level to go “low”. In the Dynamic Mode, the unit has to track at least four
satellites, for the Tracking level to go “low”, and all available satellites are used for
the time solution. The Tracking level is “high” when the unit is not acquiring data
from any satellite or the satellites are not used for the time solution (as in the
Flywheel Mode).
B. J5 - LOCKED
When this CMOS output level is “low” (LOCKED), the 1pps output is coherent to
the internal 10MHz Oscillator. The DAC voltage controls the 10MHz oscillator
from which the 1PPS is derived. When this CMOS output level is “high” (i.e., not
locked), the 1pps is constantly being corrected (jammed) to on time using the 1PPS
from the GPS Receiver Module. In this mode, the 1PPS output can jump.
C.
J6 - 1PPS
This output is a thirty to fifty
μ
sec wide pulse at CMOS levels. The rise and fall
times are
≤
6 nanoseconds. It is positive (rising) edge on time, within
±
125
nanoseconds relative to either UTC or GPS with six or more satellite averaging with
95% confidence.
D. J7 - 10MHz SINE WAVE
This output has a nominal amplitude of one volt RMS into a 50
Ω
load.
Note: The output amplitude of the 10MHz sine wave is dependent on the internal
time base. This amplitude specification is for the Voltage Controlled
Temperature Compensated Crystal oscillator.
J7 – COINCIDENCE OUTPUT (ET6500 ONLY)
The Preset Coincidence Pulse occurs 200 Nanoseconds late. Its pulse width is
approximately two (2) microseconds wide, positive edge on-time. It is capable of
driving 10 LSTTL loads.
To enable this output, on the GPS Main Assembly 100015, jumper J17 pins 7-8
(only). See Figure 2-3 in Chapter Two.
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) 1-5