In-Situ Aqua TROLL 400 Modbus and SDI-12 Reference Guide - Manual (Page 65)

8.11.9 Time
Time is represented by a 6-byte (3 register) number. The first 4 bytes represent the number of
seconds since 00:00:00 January 1, 1970 UTC, MSB first, not adjusted for DST. The 5th and 6th
bytes are fractions of a second represented by the bits in powers of 2 starting with the MSB. If a
device does not have the ability to support the full fractions of a second resolution available in
the time format, unused bits must be set to 0.
Time Example: For a time value of 0x001A5E00C000, the bytes 0x001A5E00 represent the
whole number of seconds from the reference time. The bytes 0xC000 represent the additional
fractional number of seconds as shown in the diagram above. In this example, the whole
number of seconds represents 20 days and the fractional seconds represents 750 ms.
Seconds after reference time,
MSB First, UTC
Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5
Bit 7
1/2 sec
Bit 6
1/4 sec
Bit 5
1/8 sec
Bit 4
1/16 sec
Bit 3
1/32 sec
Bit 2
1/64 sec
Bit 1
1/128 sec
Bit 0
1/256 sec
Register (N) Register (N+1) Register (N+2)
Bit 7
1/512 sec
Bit 6
1/1024 sec
Bit 4
1/4096 sec
Bit 3
1/8192 sec
Bit 2
1/16384
Bit 1
1/32768
Bit 0
1/65536
Bit 5
1/2048 sec
MSB LSB
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