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3 Special Data Input Commands
MiLLennium Command Descriptions Manual 21
$TM1A/B Receiver Time of 1PPS
The $TM1A and TM1B data messages can be used to time-synchronize multiple receivers which are all referencing
the same external oscillator. First, ensure that
SETTIMESYNC is enabled. Next, the primary unit must be sending
its 1PPS signal to the
MARKIN input of the secondary unit. Third, the two units must be communicating via a COM
port. In this configuration, the user can send the $
TM1A log from a primary to a secondary unit, in a manner similar
to that for $
ALMA or $UTCA. The secondary unit is then able to compare the time information contained in the log
with that of the 1PPS signal, and set its clock even though it may not be tracking any satellites.
The ASCII $
TM1A data message is generated from a TM1A log, and the binary TM1B data message is generated from
a
TM1B log. For descriptions of these data messages, please see the description of the TM1A/B logs in Chapter 4
and Appendix D. An example of a $
TM1A data message is as follows:
$TM1A,794,414634.999999966,-0.000000078,0.000000021,-.999999998,0*57[CR][LF]
The $TM1A/B message refers to the 1PPS pulse which has just occurred. In other words TM1A comes after a 1PPS
pulse. The length of the pulse for the 24 channel L1/L2 MiLLennium GPSCard is a normally high, active low pulse
(1 millisecond), where falling edge is reference.