MT9044AP1 Zarlink Semiconductor, Inc., MT9044AP1 Datasheet - Page 11

• Manufacturer Part Number: MT9044AP1
• Description: Framer: Framer Circuit: T1/E1/OC3 System Synchronizer
• Manufacturer: Zarlink Semiconductor, Inc.

MT9044
Data Sheet
Manual Control
Manual Control should be used when either very simple MT9044 control is required, or when complex control is
required which is not accommodated by Automatic Control. For example, very simple control could include
operation in a system which only requires Normal Mode with reference switching using only a single input stimulus
(RSEL). Very simple control would require no external circuitry. Complex control could include a system which
requires state changes between Normal, Holdover and Freerun Modes based on numerous input stimuli. Complex
control would require external circuitry, typically a microcontroller.
Under Manual Control, one of the three modes is selected by mode/control select pins MS2 and MS1. The active
reference input (PRI or SEC) is selected by the RSEL pin as shown in Table 2. Refer to Table 4 and Figure 7 for
details of the state change sequences.
Automatic Control
Automatic Control should be used when simple MT9044 control is required, which is more complex than the very
simple control provide by Manual Control with no external circuitry, but not as complex as Manual Control with a
microcontroller. For example, simple control could include operation in a system which can be accommodated by
the Automatic Control State Diagram shown in Figure 8.
Automatic Control is also selected by mode/control pins MS2 and MS1. However, the mode and active reference
source is selected automatically by the internal Automatic State Machine (See Figure 6). The mode and reference
changes are based on the logic levels on the LOS1, LOS2 and GTi control pins. Refer to Table 5 and Figure 8 for
details of the state change sequences.
Normal Mode
Normal Mode is typically used when a slave clock source, synchronized to the network is required.
In Normal Mode, the MT9044 provides timing (C1.5o, C2o, C3o, C4o, C8o, C16o, and C19) and frame
synchronization (F0o, F8o, F16o, RSP, TSP) signals, which are synchronized to one of two reference inputs (PRI or
SEC). The input reference signal may have a nominal frequency of 8kHz, 1.544MHz or 2.048MHz.
From a reset condition, the MT9044 will take up to 25 seconds for the output signal to be phase locked to the
selected reference.
The selection of input references is control dependent as shown in State Tables 4 and 5. The reference frequencies
are selected by the frequency control pins FS2 and FS1 as shown in Table 1.
Holdover Mode
Holdover Mode is typically used for short durations (e.g. 2 seconds) while network synchronization is temporarily
disrupted.
In Holdover Mode, the MT9044 provides timing and synchronization signals, which are not locked to an external
reference signal, but are based on storage techniques. The storage value is determined while the device is in
Normal Mode and locked to an external reference signal.
When in Normal Mode, and locked to the input reference signal, a numerical value corresponding to the MT9044
output frequency is stored alternately in two memory locations every 30ms. When the device is switched into
Holdover Mode, the value in memory from between 30ms and 60ms is used to set the output frequency of the
device.
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Zarlink Semiconductor Inc.