CHAPTER FOUR
4-10
bc620/627AT Time and Frequency Processor
Symmetricom, Inc.
4.1.11 PACKET “L”' - SET REAL TIME CLOCK
This packet loads the battery backed real time clock IC which is used as the source of major time
and 1pps epoch when mode 3 is selected. The format follows:
byte
1
SOH.
byte
2
“L.”
byte
3
Years Tens.
byte
4
Years Units.
byte
5
Months Tens.
byte
6
Months Units (January = month 1).
byte
7
Day of Month Tens.
byte
8
Day of Month Units.
byte
9
Hours Tens.
byte
10
Hours Units.
byte
11
Minutes Tens.
byte
12
Minutes Units.
byte
13
Seconds Tens.
byte
14
Seconds Units.
byte
15 ETB.
As usual all data is in the ASCII format. The TFP need not be in Mode 3 when packet “L”' is
downloaded.
4.1.12 PACKET “M” - LOCAL TIME OFFSET SELECT ( bc627AT GPS Mode 4 Only)
This packet allows time to be maintained with an hour offset. This situation usually arises when
the source of time is in a UTC (Universal Time Coordinated) format and the local time is
required from the TFP. The offset only applies to the hours digits. The format is as follows:
byte
1
SOH.
byte
2
“M.”
byte
3
Sign
“+” or “-”.
byte
4
Hours Tens.
byte
5
Hours Units.
byte
6
ETB.
A positive sign is from the prime meridian heading East, and a negative sign is used from the
prime meridian heading West. For example, Eastern Standard Time would be -05 relative to
UTC.
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