CHAPTER ONE
1-8
bc635VME/bc350VXI Time and Frequency Processor (Rev. E)
Symmetricom Inc
1.5.3.3 EVENT INPUT
This function allows the user to command the TFP device to monitor a hardware timing signal.
The source for the signal can be either the External Event input on the device or the output of the
Heartbeat (Periodic) mentioned earlier in this chapter. The External Event signal capture may be
set to occur on either the rising or falling edge. The Heartbeat signal capture is always on the
rising edge. When a signal occurs in the selected format, the time at which the signal occurred is
loaded into the event time registers. The capture lockout checkbox can be used to control
whether or not subsequent signals will overwrite the data in the event time registers. The output
of this circuitry is capable of creating a VME bus interrupt.
1.5.3.4 FREQUENCY OUTPUT
This function allows the user to control the frequency signal output by the TFP device. The
available frequencies are 1, 5 and 10 MHz. The default state of this output is 10MHz.
1.5.4 INTERRUPTS
This function allows the user to control the generation of VME bus interrupts by the TFP device.
If the latch event time function is enabled, the TFP will latch the time in the event time registers
when an interrupt is detected. The user may query the event time registers to see when a
particular event occurred. The latch event time function should not be enabled when external
events are selected as these already latch the time in the event registers. Three control registers
are provided to control the VME interrupts.
1.5.5 OSCILLATOR PARAMETERS
This group allows the user to select an external oscillator or the on board oscillator, in addition
to enabling/disabling disciplining and jamsyncing. If disciplining and jamsyncing are disabled,
the oscillator control DAC can be programmed to hold the oscillator control voltage to a specific
value. When the TFP is synchronized to an input time source, the oscillator will be disciplined to
the input source signal.
1.5.6 SYNC RTC TIME TO EXTERNAL TIME
This function allows the user to force the Real Time Clock (RTC) time to the board time.
1.5.7 BOARD RESET
This function allows the user to reset the TFP device. This command is useful when starting a
test or in the case that unexpected behavior is observed from the card. This function is not used
during normal operation.
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