Specifications

VP ONCORE COMMAND REFERENCE
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ALMANAC DATA OUTPUT MESSAGE (@@Be)
This parameter determines the rate the almanac data is output. The user
has the option of requesting the almanac data output one time (polled),
or each time the almanac data changes (continuously). The almanac
data output parameter set is stored in nonvolatile memory
Almanac data for the GPS satellites is transmitted in words 3 through 10
of sub-frame 5 (pages 1 through 25), and words 3 through 10 of
subframe 4 (pages 2 through 5, 7 through 10, and 25) of the satellite
broadcast data message. The user is directed to the ICD-GPS-200 for
specifics on the format of the almanac data.
The GPS receiver outputs the almanac data through a series of output
messages, each of which is identified by the particular subframe and
page. The data fields of each individual message correspond to words 3
through 10 of the broadcast data. Each word contains 24 data bits.
The entire almanac data output consists of 34 output response
messages corresponding to the 25 pages of sub frame 5 and the 9
pages in subframe 4 that contain almanac data (pages 2 through 5, 7
through 10, and 25). The total message output for one output request is
1122 bytes including the @@Be prefix and the checksum I carriage
return I Tine feed for each output. The output message begins with sub-
frame 5 page 1.
The GPS receiver will output about 750 bytes of message data for each
one second output opportunity If selected, the almanac response
message is output until the total number of bytes sent on a 1-second
epoch exceeds 750. The remainder of the almanac message is sent on
the next 1-second epoch (up to the 750 byte limit per second) until all of
the almanac data is output.
If the user issues this command and the GPS receiver does not contain
an almanac, then the GPS receiver returns one response message with
the subframe and page bytes equal to zero.
80 Synergy Systems, LLC 05OCT01