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E: Time Code Formats

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 has 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 XL-GPS 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.

Output

The XL-GPS provides the following IRIG time code outputs (refer to IRIG Standard 200-95):

IRIG-B: B120 1 kHz sine wave amplitude modulated with BCD, CF, SBS

B000 DC level shift, width coded with BCD, CF, SBS

Page 199 of 221 .................................098-00116-000 Rev. A

Symmetricom XL-GPS User Manual

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