pt7a4409 Pericom Technology Inc, pt7a4409 Datasheet - Page 11

• Manufacturer Part Number: pt7a4409
• Description: T1/e1/oc3 System Synchronizer
• Manufacturer: Pericom Technology Inc

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Manual Mode
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
PT7A4409/4409L in accordance with the State Change Diagram
shown in Figure 8.
Automatic Mode is also selected by MS2 and MS1 (set 1,1). In
this Mode, the PT7A4409/4409L will operate in three states
alternatively. The changes of states will follow a sequence au-
tomatically under control of LOS1, LOS2 and GTi. See Table 7
and Figure 8 for the state change sequence.
Normal State
In Normal State, the PT7A4409/4409L 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.
PT0103(12/05)
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Holdover State
In Holdover State, the output signals of PT7A4409/4409L 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 Hold-
over 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 negli-
gible because the Holdover State is very accurate. Two factors
affect the accuracy of Holdover State. One is drift on the Mas-
ter 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, under
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 net-
work synchronization is achieved.
In Free-Run State, the outputs of the PT7A4409/4409L are
uncorrelated with the input reference signal and the stored in-
formation of output reference. Instead, these output signals are
based solely on the master clock frequency (OSCi). The accu-
racy of the output clock is equal to the accuracy of the master
clock (OSCi).
T1/E1/OC3 System Synchronizer
PT7A4409/4409L
Data Sheet
Ver:2