Larus 80-100-280Issue 2, March 2001
AB-1
tarClock 200E System Behavior: Phase Alignment
1.
the output cards so that they
switch to use the output from the secondary card.
2.
hase should remain within a few nanoseconds of the primary card's
output.
3.
aximum for the 54573 and 54574 cards is 81 nanoseconds in
1.326 milliseconds.
Appendix B
_________________________________________
_
S
A redundant system contains two track and hold cards. The output of one is used
by the output driver cards and is referred to as the primary track and hold. The
other card is in reserve and is called the secondary track and hold. If there is a
failure of the primary track and hold card, it signals
The two track and hold cards are crossconnected via the backplane to allow each
track and hold to monitor the other one. The phase alignment feature causes the
secondary card to continually attempt to align its phase with the primary card. The
relative phase alignment is updated approximately once every 8 seconds. This
means that the secondary track and hold changes its phase very slowly as it tries
to align its output with the primary track and hold. The phase alignment process
may take many seconds initially, depending on the relative phase between the
input references being tracked by each card. Once aligned, the secondary card's
output p
The phase alignment feature minimizes the jump in phase in the system outputs
when the output driver cards switch between the two track and hold references.
The 54571, 54572, 54575, 54576, and 54577 output cards contain circuitry to limit
the output phase change rate to a maximum of 20 nanoseconds in 14
milliseconds. The m
