sepam 20 user manual - Schneider Electric

Modbus communication Time-tagging of events
Presentation
The communication system time-tags the data
prcessed by Sepam. The time-tagging function assigns
a date and precise time to status changes so that they
can be accurately classified with over time. Timetagged
data are events that can be processed in the
control room by the remote monitoring and control
system using the communication protocol for data
logging and chronological reports.
Sepam time-tags the following data:
b logic inputs
b remote annunciation bits
b information pertaining to Sepam equipment (see
Sepam check-word).
Time-tagging is carried out systematically.
Chronological sorting of the time-tagged events is
performed by the remote monitoring and control
system.
Time-tagging
Sepam time-tagging uses absolute time (see section
on date and time). When an event is detected, it is
tagged with the absolute time given by Sepam’s
internal clock.
All the Sepam internal clocks must be synchronized so
as to avoid drifts and all be the same to allow inter-
Sepam chronological sorting. Sepam has two
mechanisms for managing its internal clock:
b time-setting:
for initializing or modifying the absolute time. A special
Modbus message, called “time message”, is used to
time-set each Sepam
b synchronization:
to avoid Sepam internal clock drifts and ensure inter-
Sepam synchronization.
Internal clocks can be synchronized according to two
principles:
b internal synchronization:
via the communication network without any additional
cabling,
b external synchronization:
via a logic input with additional cabling.
At the time of commissioning, the user sets the
synchronization mode parameter.
PCRED301005EN - 06/2008
Initialization of the time-tagging function
Each time the communication system is initialized (energizing of Sepam), the events
are generated in the following order:
b appearance of "data loss"
b appearance of "incorrect time"
b appearance of "not synchronous"
b disappearance of "data loss".
The function is initialized with the current values of the remote annunciation and logic
input status without creating any events related to these data. After the initialization
phase, event detection is activated.
It can only be interrupted by saturation of the internal event storage queue or by the
presence of a major fault in Sepam.
Date and time
Presentation
An absolute date and time are generated internally by Sepam, comprising the following
information: Year: Month: Day: Hour: minute: millisecond. The date and time format
is standardized (ref.: IEC870-5-4).
Resetting the date and time
Sepam's internal clock is not saved; it needs to be time-set via the communication
network each time the Sepam is energized.
Sepam series 20's internal clock may be set in two different ways:
b by the remote monitoring and control system, via the Modbus link
b via the SFT2841 software, "general characteristics" screen.
The time that is tagged on events is encoded in 8 bytes as follows:
b15 b14 b13 b12 b11 b10 b09 b08 b07 b06 b05 b04 b03 b02 b01 b00 word
0 0 0 0 0 0 0 0 0 Y Y Y Y Y Y Y word 1
0 0 0 0 M M M M 0 0 0 D D D D D word 2
0 0 0 H H H H H 0 0 mn mn mn mn mn mn word 3
ms ms ms ms ms ms ms ms ms ms ms ms ms ms ms ms word 4
Y - 1 byte for years: varies from 0 to 99 years.
The remote monitoring and control system must ensure that the year 00 is greater
than 99.
M - 1 byte for months: varies from 1 to 12.
D - 1 byte for days: varies from 1 to 31.
H - 1 byte for hours: varies from 0 to 23.
mn - 1 byte for minutes: varies from 0 to 59.
ms - 2 bytes for milliseconds: varies from 0 to 59999.
This information is encoded in binary form. Sepam is time-set via the “write word”
function (function 16) at the address 0002 with a mandatory 4-word time message.
The bits set to “0” in the description above correspond to format fields which are not
used and not generated by Sepam.
Since these bits can be transmitted to Sepam with random values, Sepam performs
the necessary disabling.
Sepam does not check the consistency or validity of the date and time received.
Synchronization clock
A synchronization clock is required for setting the date and time of Sepam.
Schneider Electric has tested the following equipment:
Gorgy Timing, ref. RT 300, equipped with the M540 module.
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