ISU AT Command Reference

ISU AT Command ReferencePhase III AT Commands7.17 -MSSTM - Request System TimeExec Command: -MSSTMQuery the latest system time received from the network. The response is the form:-MSSTM: can take one of the following forms:no network service The ISU has not yet received system time from the network.XXXXXXXWhere XXXXXXXX is the current Iridium system time available fromthe network. The system time as received through the Iridium AirInterface, is a 32 bit integer count of the number of 90 millisecondintervals that have elapsed since the epoch. The return value isformatted as an ASCII hexadecimal number. The counter will rolloverapproximately every 12 years.Iridium system time epoch: June 1, 1996, 00:00:11 (GMT):Iridium system time source: The system time is available and valid only after the ISU has registered withthe network and has received the Iridium system time from the network. Once the time is received, the ISUuses its internal clock to increment the counter. In addition, at least every 8 hours, or on location update orother event that requires re-registration, the ISU will obtain a new system time from the network.Time localization: None. The system time value is always expressed in GMT time.Resolution and accuracy: The resolution of the system time is one Iridium frame tick, or 90 ms. Accuracyas measured by the difference between the time reported and the actual time it is sent out the ISU’s serialport should not exceed 4 frame ticks (.36 seconds) and in most cases will be one frame tick (.09 seconds) orless.Version 2.6March 30, 2006 56