pt7a4402b Pericom Technology Inc, pt7a4402b Datasheet - Page 10

• Manufacturer Part Number: pt7a4402b
• Description: T1/e1 System Synchronizer
• Manufacturer: Pericom Technology Inc

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Mode/State Control Machine
The Mode/State Control Machine determines whether the
PT7A4402B/4402L operates in Automatic or Manual mode, and
whether it is in the Normal, Holdover or Free-Run state. In Au-
tomatic Mode, the PT7A4402B/4402L selects one of three states,
Normal, Holdover or Free-Run State. The sequence is deter-
mined by LOS1, LOS2 and GTi signals. In Manual Mode, a
single state of operation is selected, in accordance with the
MS1, MS2, GTi and RSEL signals.
All mode and state changes are synchronous with the rising
edge of F8. See the Modes and States of Operation section for
complete details.
Guard Time Circuit
The Guard Time Circuit sends control signal (GTi) to Mode/
State Control Machine for control of Modes and States. It has
two functions:
Under Automatic Mode and in Primary Normal State, two state
changes are possible (not counting Auto-Holdover). They are:
The level at the GTi pin determines which state occurs. When
Input Impairment Monitor
This circuit monitors the input signals to the DPLL and auto-
matically enables the Holdover State (Auto-Holdover) when
the incoming signal is completely lost, or if its frequency is
outside the auto-holdover capture range (either a small or large
amount). When the incoming signal returns to normal, the DPLL
will be returned to Normal State.
The Auto-Holdover circuit does not use TIE correction. There-
fore, the phase delay between the input and output after switch-
ing back to Normal State is preserved (is the same as just prior
to the switch to Auto-Holdover).
PT0100(12/05)
- Primary Normal to Primary Holdover, and
- Primary Normal to Secondary Normal.
- GTi=0, Primary Normal to Primary Holdover,
- GTi=1, Primary Normal to Secondary Normal.
- enabling/disabling the TIE Corrector (Manual and Au-
- selecting which mode change takes place (Automatic
tomatic) (Refer to Table 6 and 7);
only).
10
Modes and States of Operation
The PT7A4402B/4402L operates either in Manual mode or Au-
tomatic mode. Each mode has three possible operating states,
Normal, Holdover or Free-Run.
Shown in Table 4 and Table 5 are the mode and state selection
instructions, using pins MS1, MS2, and RSEL.
Table 4. Input Reference Selection
Table 5. Operation Modes and States
M 2 S
M 2 S
M 2 S
M 2 S
M
M
M
M
M
M
M
A
0
0
1
1
2 S
a
d o
d o
d o
d o
d o
u
u n
o t
s e
s e
s e
s e
s e
l a
M 1 S
M 1 S
M 1 S
M 1 S
M
0
0
1
1
1 S
R
R
R
R
R
S
S
S
S
S
T1/E1 System Synchronizer
0
0
1
1
E
E
E
E
E
L
L
L
L
L
M
M
M
M
M
M
M
M
A
a
a
a
d o
d o
d o
d o
d o
u
u n
u n
u n
M
o t
s e
s e
s e
s e
s e
l a
l a
l a
o
PT7A4402B/4402L
e d
S /
I
I
I
I
I
p n
p n
p n
p n
p n
a t
t u
t u
t u
e t
M
t u
t u
R
e
c a
M
S
M
R
R
R
R
R
P
e s
H
E
I R
i h
F
N
f e
f e
f e
f e
f e
c a
o
Data Sheet
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t S
t S
t S
t S
t S
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C
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d l
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t a
t a
t a
t a
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m
S /
v o
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n e
n e
n e
n e
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C
s e
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C
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Ver:1