Symmetricom XLi IEEE 1588 manual IRIG-B Time Quality Flags, Output, Input

SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

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.

Output

The XLi 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

IRIG-A: A133 1 KHz sine wave amplitude modulated with BCD, SBS

A003 DC level shift, width coded with BCD, SBS

Input

The XLi can also synchronize and lock to IRIG-B and IRIG-A input codes. The required input code does not need to have the CF or SBS elements. The XLi only decodes the BCD portion of the incoming code.

IRIG-B: B122 1 kHz sine wave amplitude modulated with BCD

B002 DC level shift, width coded with BCD

IRIG-A: A132 10 kHz sine wave amplitude modulated with BCD, SBS

A002 DC level shift, width coded with BCD, SBS

NASA 36

Introduction

The NASA 36 time code is similar to the previously mentioned IRIG codes. The NASA 36 code frame also contains 100 bit elements like the IRIG codes. In the strict sense, NASA 36 encodes Universal

190 XLi IEEE 1588 Clock

997-01510-03, Rev. C, 12/12/2006