Siemens SIMATIC ET 200M Operating Instructions Manual page 154

Functions
8.2 Time stamping the input signals with IM 153-2
Structure of a special message
A special message always comes from the IM 153-2 (slot 2). It is structured as follows:
Table 8- 7 Structure of a special message
Meaning
Slot number of the
IM 153-2
Code of the special mes-
sage
Property for special mes-
sage
Reserved
Time of the special mes-
sage
Structure of a time stamp in the ISP format
A time stamp in the ISP format is structured as follows:
Table 8- 8
Byte
0 ... 3
4 ... 7
154
Number of Remarks
bytes
1 Always "2" in the case of a special message
1 01h
02h
03h
04h
05h
06h
07h
08h
1 01h
01h
01h
1 Unassigned
8 (2 DW) Time stamp in ISP-format
(refer to table below for structure)
Structure of a time stamp in the ISP format
Contents
Seconds as of 01.01.1900; 0:00:00,000 o´clock
Fractions of a second in multiples of 1/(2
Start-up data (a)
Time message frame failure: the following signal messages have,
among others, a precision that is less than 10 ms (b)
not used
Time difference between message frame and internal clock > 10 ms
(c)
(message always occurs as a message pair)
STOP of the time stamping (b)
Buffer overflow: the following signal messages are lost until the buff-
er is clear again (b)
Changeover in the case of redundancy (a)
Loss of information in the case of redundancy (b)
(internal error)
(a) BEGIN
(b) INCOMING
(c)
internal time of the
IM 153-2 at the mo-
ment of synchroniza-
tion
From the message pair of the special message (c) it can be seen
whether the internal clock has been put back or forward and how
great the time difference was during at the synchronization.
) s
32
Operating Instructions, 04/2022, EWA-4NEB7806006-09
00h (a) END
00h (b) OUTGOING
00h (c)
Synchronization time to which the
internal clock of the IM 153-2 is
set
range
in accordance with
01.01.1900 ... 06.02.2036
0 ... < 1 s
ET 200M