SM3 Datasheet, PDF (2/36 Pages) Connor-Winfield Corporation – ULTRA MINIATURE STRATUM 3 MODULE

General Description
The SM3 timing module provides a clock output that meets or exceeds Stratum 3 specifications given in GR-1244-CORE (Issue 2),
GR-253-CORE (Issue 3), ITU-T G.812 (Type 3) and ITU-T G813 (Option 2). The SM3 features four reference inputs that will
auto-detect the following reference frequencies: 8 kHz, 1.544 MHz, 2.048 MHz, 12.96 MHz, 19.44 MHz, 25.92 MHz, 38.88 MHz,
51.84 MHz and 77.76 MHz.
The SM3 timing module can be configured during production to produce an output up to 77.76 MHz. This output is derived from
an onboard VCXO and must be specified when ordering. The BITS output selectable for either 1.544 or 2.048 MHz. The master/
slave output is 8KHz. The user communicates with the SM3 module through a SPI port. The user controls the SM3 operation by
writing to the appropriate registers . The user can also enable or disable SPI operation through a SPI_Enable pin.
The SM3 offers a wide range of options for the system designer. The bandwidth is SPI Por t-selectable from 0.025 Hz to 1.6 Hz.
0.098 Hz is the recommended operational bandwidth for SONET Minimum Clock and most Stratum 3 applications. The 8 kHz out-
put has an adjustable pulse width. The pull-in range is also adjustable to establish the desired reference frequency rejection lim-
its. A Free Run frequency calibration value can be written to the module to provide a high degree of accuracy in the free run mode.
The reference frequency for any given reference input is automatically detected. A wealth of status information is available
through the SPI Port registers. The user also has a choice between autonomous or full manual control operation.
In manual mode, the user controls the module operating modes Free Run, Hold Over or locked to a specific reference in nor-
mal mode. If the chosen reference is unavailable or disqualified the module automatically enters Hold Over.
In autonomous control mode, operational mode selection occurs automatically based on reference priority and qualification
status. When the active reference becomes disqualified, the module will switch to another qualified reference. If none is available,
it will switch to Holdover. In the revertive mode the module will seek to acquire the highest priority qualified reference. In the non-
revertive mode the module will not return to the previous reference even after it is re-qualified unless there are no other qualified
references.
Switching between references is hitless. Likewise, the output frequency slew rate is minimized during any change of operating
mode, including entry into and return from Free Run or Hold Over to protect traffic from transient-induced bit errors.
Reference Status information and the operating mode information is accessed through status registers. The module will set the
Interrupt pin (SPI_INT) low to indicate a status change. An Alarm pin is used to indicate failure of the active reference status.
Free Run operation guarantees an output within 4.6ppm of nominal frequency and Holdover operation guarantees the output
frequency will not change by more than 0.37ppm during the first 24 hours. Frequency accuracy is based on a TCXO for its small
size, low power consumption and outstanding performance over all environmental conditions.
The module operates on 3.3V ± 5% with a typical power draw of less than 500 milliwatts. The module operates over the 0° to
70°C commercial temperature range.
Figure 1
TRST
TCK
TDO
TDI
TMS
M/S REF
4
REF 1 - 4
RESET
MASTER SELECT
T1/E1
SPI_ENBL
SPI_CLK
SPI_IN
SPI_OUT
SPI_INT
Functional Block Diagram
OCXO
EEPROM
DAC
VCXO
Reference Input Monitor
Control
Mode
Reference
Selection
Reference Priority,
Revertivity and Mask
Table
DPLL
Bus Interface
APLL
OUTPUT1
M/S_OUT
BITS_CLK
LOS
LOL
HOLD_GOOD
Data Sheet #: TM052 Page 2 of 36 Rev: 03 Date: 11/07/08
© Copyright 2008 The Connor-Winfield Corp. All Rights Reserved Specifications subject to change without notice