I believe that the NMEA sentence you have referenced is a proprietary, manufacturer specific message. In this case it is defined for Trimble navigation Ltd. (TNL) receivers, which happen to be what I have as well. However, I would caution against using this for any application that you want to have wider applicability, as most receivers available to the cost conscious user will be restricted to the common, generic NMEA messages. Some receivers can output time to 1/10 second in the generic messages, such as $GPGLL or $GPRMC (...,hhmmss.s,...) but you can't count on this for all receivers.

These time stamps are actually the time for which the position fix is calculated (in the past) and do not represent the time at which you actually receive the message on the serial port. You can make an adjustment to compensate for the typical time required to calculate the solution and communicate it to the receiving device but you will not achieve sub-second accuracy that way. The only way to get sub-second accuracy reliably would be to use the pulse-per-second output available from some receivers, but, as previously discussed above, that would reguire a discrete signal input and probably an interrupt on the Empeg, dedicated to achieving reasonable accuracy.

Lynn