INTRODUCTION
Symmetricom Inc
bc635VME/bc350VXI Time and Frequency Processor (Rev. E)
1-5
1.5.1.2 TIME FORMAT
The event time capture and time registers of the TFP default to the decimal time format. The
major time registers are divided into 4 bit fields for each decimal digit of days, hours minutes
and seconds. For the GPS mode only, the time registers can operate in the binary format where
major time is represented as seconds since the GPS epoch.
1.5.1.3 SET TIME
This function allows the user to set the time on the TFP device. Decimal time values can be
entered into the time registers. This function is typically used when operating in either the
Freerunning or External 1PPS modes. While the function may be used when operating in Time
code or GPS modes, subsequent time data received from the selected reference source will
overwrite the loaded time.
1.5.1.4 SET YEAR
This function allows the user to set the year data. Typically, this function is used when the board
is operating in time code decoding mode. Many time code formats (including standard IRIG B)
do not include year information in the data. Using this function will allow the TFP device to
extract the time of year data from the time code source while using year information provided by
the user. The board will decode the year and roll over the days for a leap year (365-366-001) or a
non-leap year (365-001). The supported range is 1990 – 2037. The board will follow the input
time source if the input rollover day sequence does not match the board rollover day sequence as
defined by the programmed year.
1.5.1.5 SET LOCAL OFFSET
This function allows the user to program a local offset of 1-hour increments into the TFP device.
If the local offset value is nonzero, the device will adjust any reference timing information in
order to maintain a local time in TFP clock. Use of this function only affects the time data in the
TIME registers described in paragraph 3.1.
1.5.1.6 SET PROPAGATION DELAY
This function allows the user to command the TFP device to compensate for propagation delays
introduced by the currently selected reference source. For example, when the unit is operating in
Time code decoding mode, a long cable run could result in the input time code having a
propagation delay. The delay value is programmable in units of 100ns and has an allowed range
from –9999999 t9999999.
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