PT7A4410 Datasheet, PDF (11/34 Pages) List of Unclassifed Manufacturers – T1/E1/OC3 System Synchronizer

Data Sheet
PT7A4410/4410L
T1/E1/OC3 System Synchronizer
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Manual Mode
Holdover State
The Manual Operation Mode is used when either very simple
control is required, or when complex control is required which
is not accommodated by Automatic Mode. For example,
Manual Mode can be used in a system requiring only Normal
State and only one input stimulus (RSEL). Complex control is
used for systems requiring states of operation and more input
stimuli. In such cases, external circuitry, typically a
microcontroller, is needed.
In Manual Mode, one of the three states is selected by MS2
and MS1. The active reference input is selected by the RSEL
pin. See Table 4 and Table 5. For the state change situation,
refer to Table 6 and Figure 7.
Automatic Mode
Automatic Mode is used in systems requiring neither very
simple nor very complex control, which can be realized by the
PT7A4410/4410L in accordance with the State Change Dia-
gram shown in Figure 8.
Automatic Mode is also selected by MS2 and MS1 (set 1,1). In
this Mode, the PT7A4410/4410L will operate in three states
alternatively. The changes of states will follow a sequence
automatically under control of LOS1, LOS2 and GTi. See Table
7 and Figure 8 for the state change sequence.
Normal State
In Normal State, the PT7A4410/4410L output signals are syn-
chronized with one of two input reference inputs.
In this state, the input reference signal is used, with or without
TIE correction, as reference for the DPLL phase detector.
In Holdover State, the output signals of PT7A4410/4410L are
not synchronized with the external input reference signal. In-
stead, they are generated by using the information stored 30ms
to 60ms before when the device operated in Normal State.
When in Normal Mode, a numerical value corresponding to
the output reference frequency is stored alternately in two
memory locations every 30ms. When the device is switched
into Holdover state, the value in memory from (between 30ms
and 60ms) is used to set the output frequency of the device.
Generally, the amount of phase drift while in Holdover is neg-
ligible because the Holdover State is very accurate. Two fac-
tors affect the accuracy of Holdover State. One is drift on the
Master Clock while in Holdover State. The change in OSCi
accuracy while in Holdover, other than absolute Master Clock
(OSCi) accuracy, will affect the holdover accuracy. The other
factor is large jitter on the reference input prior (30 to 60ms) to
the mode switch.
The Holdover State is generally used for short durations, un-
der control of GTi signal, when the synchronization to the
input reference is temporarily disturbed.
Free-Run State
Typically the Free-Run State is used when a master clock is
required or immediately following system power-up before
network synchronization is achieved.
In Free-Run State, the outputs of the PT7A4410/4410L are
uncorrelated with the input reference signal and the stored
information of output reference. Instead, these output signals
are based solely on the master clock frequency (OSCi). The
accuracy of the output clock is equal to the accuracy of the
master clock (OSCi).
PT0106(09/02)
11
Ver:0