Overview
E: Time Code Formats
The following section provides a summary description of the three time code types used by
the XL-GPS. The definitive IRIG time code specification, the Range Commanders Council’s
IRIG Serial Time Code Formats, IRIG Standard 200-04.
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 XL-GPS.
IRIG
Introduction
The document 200-04 "IRIG STANDARD TIME FORMATS" by the Telecommunications
Working Group, Inter range Instrumentation Group, Range Commanders Council describes
IRIG-B time code.
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 XL-
GPS is suitable for remote display driving, magnetic tape recording and many other uses.
IRIG codes, in the strict sense, encode Coordinated Universal 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 page200. The level shifted, pulse width modulated,
serial formats of IRIG-B 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 XL-GPS, this segment encodes worst case time error flags as
explained below. The third segment sometimes encodes time of day in straight binary
seconds (SBS) notation. Both IRIG-B encodes SBS on the Model XL-GPS.
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.
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
098-00116-000 Rev. A............................... Page 198 of 221
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