The setting changes performed by either of the two operations defined above are made to the scratchpad
area. These changes must be confirmed by writing to register 4x0405.
The active protection setting groups can be selected by writing to register 40404. An illegal data response
will be returned if an attempt is made to set the active group to one that has been disabled.
9.10 TIME SYNCHRONISATION
The date-time data type G12 allows real date and time information to be conveyed to a resolution of 1
ms.
The structure of the data type is compliant with the IEC 60870-5-4 Binary Time 2a format.
The seven bytes of the date/time frame are packed into four 16-bit registers and are transmitted in sequence
starting from byte 1. This is followed by a null byte, making eight bytes in total.
Register data is usually transmitted starting with the highest-order byte. Therefore byte 1 will be in the high-
order byte position followed by byte 2 in the low-order position for the first register. The last register will
contain just byte 7 in the high order position and the low order byte will have a value of zero.
G12 date & time data type structure
Bit Position
Byte 7 6 5 4 3 2 1 0
1 m7 m6 m5 m4 m3 m2 m1 m0
2 m15 m14 m13 m12 m11 m10 m9 m8
3 IV R I5 I4 I3 I2 I1 I0
4 SU R R H4 H3 H2 H1 H0
5 W2 W1 W0 D4 D3 D2 D1 D0
6 R R R R M3 M2 M1 M0
7 R Y6 Y5 Y4 Y3 Y2 Y1 Y0
Key to table:
● m = milliseconds: 0 to 59,999
● I = minutes: 0 to 59
● H = hours: 0 to 23
● W = day of the week: 1 to 7 starting from Monday
● D = day of the month: 1 to 31
● M = month of the year: 1 to 12 starting from January
● Y = year of the century: 0 to 99
● R = reserved: 0
● SU = summertime: 0 = GMT, 1 = summertime
● IV = invalid: 0 = invalid value, 1 = valid value
Since the range of the data type is only 100 years, the century must be deduced. The century is calculated
as the one that will produce the nearest time value to the current date. For example: 30-12-99 is 30-12-1999
when received in 1999 & 2000, but is 30-12-2099 when received in 2050. This technique allows 2 digit years
to be accurately converted to 4 digits in a ±50 year window around the current date.
The invalid bit has two applications:
● It can indicate that the date-time information is considered inaccurate, but is the best information
available.
● It can indicate that the date-time information is not available.
MiCOM P747 Chapter 7 - SCADA Communications
P747-TM-EN-1 221
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