E: Time Code Formats; Overview; Irig; Introduction - Symmetricom XLi IEEE 1588 User Manual

Symmetricom xli ieee 1588 clock user guide

Table of Contents

E: Time Code Formats

The following section provides a summary description of the three time code types used by the XLi. The

definitive IRIG time code specification, the Range Commanders Council's IRIG Serial Time Code

Formats, IRIG Standard 200-98, is available on the Web at

Overview

Please refer to the Input and Output specifications in the front of the manual for details regarding the

voltage amplitudes / modulation ratios of the following time codes provided or used by the Model XLi.

IRIG

Introduction

The document 200 95 "IRIG STANDARD TIME FORMATS" by the Telecommunications Working Group,

Inter range Instrumentation Group, Range Commanders Council describes IRIG-B and IRIG-A time

codes.

The standard time formats of IRIG codes were designed for use in missile, satellite and space research

programs. Use of these codes facilitates efficient interchange of test data. These formats are suitable

for recording on magnetic tape, oscillographs, film and for real time transmission in both automatic and

manual data reduction. IRIG-B from the Model XLi is suitable for remote display driving, magnetic tape

recording and many other uses. IRIG codes, in the strict sense, encode Universal Coordinated Time

(UTC) in 24 hour format and not local time. Nonetheless, this instrument can encode UTC or local time

in either 24 or 12 hour formats.

IRIG Code Format

Reference

"IRIG Standard Format A" on page

formats of IRIG-B and IRIG-A are divided into three segments. The first segment encodes time of year

in binary coded decimal (BCD) notation. The second segment encodes control functions. This segment

is generally available for data of the user's choice. In the IRIG-B code output of Model XLi, this segment

encodes worst case time error flags as explained below. The IRIG-A output from Model XLi does not

include control functions. The third segment sometimes encodes time of day in straight binary seconds

(SBS) notation. Both IRIG-B and IRIG-A encode SBS on the Model XLi.

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.

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

XLi IEEE 1588 Clock

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

http://jcs.mil/RCC/manuals/200/

192. The level shifted, pulse width modulated, serial

189

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E: Time Code Formats; Overview; Irig; Introduction - Symmetricom XLi IEEE 1588 User Manual