Spectracom TSync-PCIe, Руководство пользователя

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intended to support the Spectracom 91xx and 92xx IRIG formats, which use the BCDYEAR in
the Control field.
6.1.3 External 1PPS Reference
The board’s external 1PPS reference provides the on-time-point for the current second. This ref
erence is used by the TSync-PCIe as the primary source of frequency synchronization (while
another input reference is required to serve as the source of time and date information). The
external 1PPS reference can be set to use either the rising or falling edge.
6.1.4 Built-in References
The TSync-PCIe board provides built-in references that support specialized user applications.
6.1.4.1 Host Reference
The TSync-PCIe can be set to use the host as the source of date and time information, while
another input reference is required to serve as the source of frequency input. This allows the
host to provide time to the board while providing a means to determine and indicate whether
that time is valid for synchronization. Using the host as a reference means it could conceivably
be used to receive date and time information from a source not available to the board, provid
ing that information to the board for synchronization to it (while using a separate frequency
input).
6.1.4.2 Self Reference
The TSync-PCIe provides a built-in reference that allows the board to operate without a sep
arate input reference. The date and time or frequency information from this self reference is
always considered valid. This allows a user to operate the board as if it were synchronizing to
an input reference, without a valid external reference input. The self reference priority table
entry defaults to “disabled.”
6.2 Input Reference Monitor
The input reference monitor subsystem maintains the reference priority table and determines
which input reference(s) are selected to synchronize the clock subsystem.
Three tables are maintained by the system:
A default table, which provides the default reference pairings in timing accuracy priority
A working table, which is the table used for selecting reference inputs
A user table, which can be stored persistently and, if present, will be loaded into the
working table at startup
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Instruction Manual XYZ Rev. R
6.2 Input Reference Monitor