brief IRIG-B code description
HGB, 12/12/96
The following brief description about the IRIG-B code is based on the
specification of the primary Super-Kamiokande GPS
system. The system consists of components made by
TrueTime Inc.:
XL-DC GPS Time & Frequency Receiver,
a 2-km optical fiber, and a VME-SG Sync
Generator.
The "IRIG-B" pulse code contains one "frame" of 100 "elements" per
second for the time of the year and GPS receiver status.
A frame is described as:
"frame" length = 1 second.
"element" length = 10 msec.
Three types of elements are defined:
- binary zero ("0"),
- binary one ("1") and
- position marker ("P").
Each frame starts with two consecutive position markers, used as
a frame reference marker ("R"). Furthermore, a frame is divided into
10 "sets" of 10 elements each. Each "set" contains 2 BCD-coded binary
numbers (4-bit decimal), separated by a "0" from each other and
terminated by a position marker as the 10th element. The sets
contain the time of year and status bits in the following order:
- seconds (0...59),
- minutes (0...59),
- hours (0...23),
- days (0...99),
- days*100 (0...3).
- status word:
- 4th element = Lock indicator (*)
- 6th element = Threshold indicator 1 (**)
- 7th element = Threshold indicator 2 (**)
- 8th element = Threshold indicator 3 (**)
- 9th element = Threshold indicator 4 (**)
- all other elements = "0"
- n/a
- n/a
- n/a
- n/a
- (*):
- "0" = receiver locked to at least one satellite,
"1" = no satellites.
- (**):
- Worst-case threshold indicators for time quality
indication (see TrueTime manual).
Click here for an example of such an
IRIG-B frame.
More detailed info about the IRIG-B code is provided by
TECNET /
JIST3: