Irig-B Time Quality Flags; Xli Irig Time Code Input/Output - Symmetricom XLi User Manual

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The three code segments are contained within one "frame". The frame length for IRIG-B is 1 second
long and contains 100 "elements" (pulses) each of which start every 10 milliseconds. The frame length
for IRIG-A is 1/10 seconds and contains 100 elements each of which starts every 1 millisecond.
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An element may represent either a binary zero, a binary one, a reference marker or a position identifier.
A zero is 0.2 of the duration of an element, a one is 0.5 of the duration of an element and a position
identifier or reference marker is 0.8 of the duration of an element. A reference marker locates the
beginning of each frame and a position identifier marks the end of every ten elements. IRIG-B and IRIG-
A have ten position identifiers per frame.
The elements prior to position identifier P5 comprise the time of year segment. The first ten elements
encode the seconds, the second ten elements encode the minutes and so on through days. Each
element is a digit in a binary number with a place value sequence 1 2 4 8.

IRIG-B Time Quality Flags

Five flags are encoded in the control function segment of the IRIG-B code. The first flag encoded at
element P5+40ms is the LOCK indicator. It is a binary 1 when the XLi is not locked to a reference. The
second flag encoded at element P5+60ms is a binary 1 when the worst case time error exceeds
threshold 1 (refer to "Function 5 -- Time Quality Enable/Setup"). Element P5+70ms is a binary 1 when
the worst case time error exceeds threshold 2. Element P5+80ms encodes a binary 1 when the error
exceeds threshold 3 and P5+90ms when the error exceeds threshold 4.

XLi IRIG Time Code Input/Output

The XLi generates and decodes the following IRIG timecodes compliant with the IRIG 200-04 Standard
or IEEE 1344 standard:
IRIG-B: B120
B120 1344
(year), leap second, DST, time offset, time quality
B000
B000 1344
leap second, DST, time offset, time quality
IRIG-A: A130
A000
288
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1kHz sine wave amplitude modulated with BCD (time of year),CF, SBS
1kHz sine wave amplitude modulated with BCD (time of year),CF, SBS, BCD
DC level shift, pulse width coded with BCD (time of year), CF, SBS
DC level shift, pulse width coded with BCD (time of year), CF, SBS, BCD (year),
10 kHz sine wave amplitude modulated with BCD (time of year), CF, SBS
DC level shift, pulse width coded with BCD (time of year), CF, SBS
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XLi Time & Frequency System
XLi-man, Issue 8, 6/17/2008, Rev. H
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