Sensor Electronics SEC Millenium Series Instruction And Operation Manual page 379

The SEC 3120 supports multiple write holding sensor and unit registers as shown
in table 12 above. To avoid accidentally writing to any of these registers, a password is
required. For most registers (as designated in the table above) 4000 hex (16384 decimal)
must be added to the register value as a password.
For floating point register sets, the first register in the trio is the password enable
register. This register must have the Hex value 4259 written to it first, followed by the
high word and then the low word of the 32-bit IEEE floating point encoded value, using
at leas one multiple write operation.
Parameter registers low, mid, and high alarm set points and calibration value must
be less than the full scale (range) of measurement.
When setting the new clock time, registers 42912-17 are written first,
followed by 42918 to actually set the time (copy new values to clock and run).
SEC 3120 16-bit Modbus Manual
For Version 1.2 and above
Page 40 Of 46 Sensor Electronics Corporation
December 2012 P/N 1580282, Rev. 1, 20121228