ashtech HDS800, Reference Manual

Page: 52 / 678

36
Receiver Description
1PPS Output
This output delivers a periodic signal that is a multiple or
submultiple of 1 second of GPS time, with or without offset.
Using the 1PPS output is a standard feature of the receiver
(no firmware option needed).
The 1PPS output is available on port A, pin 7, whatever the
current configuration of this port (RS232 or RS422).
You can set the properties of the 1PPS signal using the
$PASHS,PPS command. These properties are:
• Period: a multiple (1 to 60) or submultiple (0.1 to 1 in
0.1-second increments) of 1 second of GPS time.
• Offset: Amount of time in seconds before (+?) or after (-?)
a full second of GPS time.
• Active edge, i.e. the edge (falling or rising) synchronized
with GPS time. (On the diagram above, the rising edge was
set to be the active edge)
You can read the current properties of the 1PPS output using
the $PASHR,PPS command.
The signal specifications for the 1PPS output are the
following:
• Signal level: 0-5 V
• Pulse duration: 1 ms
• Jitter: < 100 ns
• Slope transient time: < 20 ns
You can also output the exact GPS time of the active edge of
the 1PPS output signal using the $PASHR,PTT command.
The receiver will respond to this command right after the next
1PPS signal is issued, taking into account the chosen offset.
1PPS with
Offset= 0
GPS time
1PPS with
Offset= -
x.x sec
1PPS with
Offset= +
x.x sec
+
_