1.
3.4.4 Frequency Control Signal
The SA.22c frequency control signal is an analog input between 0 Vdc and 5 Vdc that is enabled or
disabled at the factory (making it a default setting) or by the customer at a later date (using the MSIP).
The service BIT can be selectable high or low.
When in use, the smallest incremental frequency change is 2 × 10 . The unit always powers up to the
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preset free running factory set frequency. Adjustments to the frequency are always relative to the free
running frequency of the unit (see also ).Analog Frequency Control (see page 10)
3.4.5 ACMOS Output Frequency
The ACMOS output frequency is equal to the internal crystal frequency divided by 2N (N is a number
from 1 to 65536). For more information on the list of specific ACMOS output frequencies, contact
Microsemi sales representatives.
3.4.6 Analog Frequency Control
Analog frequency adjustment range is ±1.5 × 10 (0 V–5 V into 5 kΩ). The external frequency control
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circuitry is designed so that with no voltage applied at Pin 5, the voltage self biases to mid-range or
2.5 V. This input is turned off via the MSIP to eliminate any source of noise. In some versions of the SA.
22c, this function is turned off by customer request on power up. If it is to be used later, it must be
enabled through the MSIP (refer to ).Appendix: Microsemi Serial Interface Protocol (see page 25)
The external analog frequency control is a sampled input with a typical response time constant of
154 ms.
Note: An expanded control range version of SA.22c is also available. It can provide frequency
adjustment of ±6.5 × 10 (0 V–5 V into 5 kΩ).
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3.5 Modifiable Unit Settings
SA.22c operation can be modified. See and Appendix: Using the Developer’s Kit (see page 16)
for information on how to use the MSIP to Appendix: Microsemi Serial Interface Protocol (see page 25)
use these functions.
Note: Default power up conditions cannot be altered.
The following table provides the information on the hardware and software items along with its action.
Table 4 • Hardware and Software Selectable Items
Item Action
Hardware
1PPS output enable Turn 1PPS output on or off
Software
Analog frequency adjust Enable or disable frequency control function
Adjust frequency
1
Adjust output frequency from the factory preset value
HELP Displays the help menu
View control register Displays current settings of the control register
Set control register Enable or disable outputs
View unit information Displays SA.22c information stored in the firmware
View health monitor data Displays history file of error or fault information
Minimum frequency change is 2 × 10 . Values less than this are ignored. Maximum frequency
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change, is not constrained. Setting the frequency outside of its operating limits may render the unit
non-functional.
3.6 Susceptibility to Input Noise
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