X
X
L
L
D
D
C
C
M
M
A
A
N
N
.
.
d
d
o
o
c
c
8
8
-
-
1
1
R
R
E
E
V
V
E
E
SECTION VIII
IRIG B, IRIG H (OPTION) AND IRIG E (OPTION) TIME CODE FORMAT
8-1 INTRODUCTION
The document 200-70 "IRIG STANDARD TIME FORMATS" by the Telecommunications Working
Group, Inter-range Instrumentation Group, Range Commanders Council describes IRIG B, IRIG H and
IRIG E time codes. It is available by writing Secretariat, Range Commanders Council, White Sands
Missile Range, New Mexico, 88002.
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-DC 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.
8-2 IRIG CODE FORMAT
Reference figures 8-1, 8-2 and 8-3. The level shifted, pulse-width modulated, serial formats of IRIG B,
IRIG H and IRIG E 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-DC, this
segment may encode worst-case time error flags as explained below. Neither the IRIG H (OPTION) or
IRIG E (OPTION) output from Model XL-DC encode control functions. The third segment sometimes
encodes time-of-day in straight binary seconds (SBS) notation. This segment is not encoded by the
Model XL-DC.
These three 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 E is 10 seconds and contains 100 elements each of which starts every 100 milliseconds. The
frame length for IRIG H is 1 minute long and contains 60 elements each of which starts on the second.
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 E have ten position identifiers per frame and IRIG H has six.
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.
Summary of Contents for 151-600
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