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MODBUS SCT PPU communication protocol

Supported device types and versions
Communication line configuration
Communication station configuration
I/O tag configuration
Literature
Changes and modifications
Document revisions

Supported device types and versions


This protocol supports the communication with the telemetric stations for remote measurement on gas meters of SCT company. It ensures the parallel measurement of data from the meters for wholesale gas consumption and medium one of SPP-Distribúcia a.s. .

Communication line configuration


Communication station configuration


  • Communication protocol "MODBUS SCT PPU".
  • Station address is a decimal number in the range of 0 to 255 (usually 1).

Station protocol parameters

Communication station - configuration dialog box - tab Protocol parameters.
These parameters influence some of optional protocol parameters. You can define the following station parameters:

Table 1

Parameter Meaning Units Default value
Retry Count Maximum retries of call. If any response is not received after these callings, the station switches to the communication error state. - 2
Retry Timeout Timeout before the retrying the call if any response has not been received. ms 500
Wait First Timeout Timeout between sending the call and first reading the response. ms 200
Wait Timeout Timeout between the response readings. ms 200
Max. Wait Retry Maximum retries of reading the response. - 30
Send Valid Data Only Send only valid data to D2000 System kernel. If it is set on YES, the Invalid values are not send to the system. YES/NO YES
Future Data Filter Filtering data that has a time stamp shifted forward by this value from the current time (in hours). The setting on 0 hours switches off this filter. 0-168 hours 24
History Data Filter Filtering data that have the time stamp shifted back by this parameter from the current time (in days). The setting on 0 days switches off this filter. 0-730 days 31
Full debug Extra debug information about communication on the line including debug information about all gained I/O tag values. YES/NO NO

I/O tag configuration


I/O tags for non-variable mode: Ai,Ci,TiA


I/o tag address:

Table 2 contains the list of supported I/O tag addresses. The address is in the text format - the value from the column "Address".

Table 2

Address Value type Tech. units Meaning
VER Ci - Protocol version (0x01).
ECSID Ci - ID of conversion device, it is numbered from 0.
RTURDTM TiA - RTU  time of last reading the current data from the conversion devices.
ECSDTM TiA - Time on the conversion device when the last reading the current data.
P Ai kPa Current absolute pressure.
T Ai °C Current temperature.
F Ai m3/hour Instantaneous flow.
CLO Ai m3 Current status of counter for calculated quantity of LO.
CHI Ai m3 Current status of counter for calculated quantity of HI.
C Ai m3 Current status of counter for calculated quantity, calculated as C = 10000 * CHI + CLO.
C8LO Ai m3 Status of counter for calculated quantity at 8:00 - LO.
C8HI Ai m3 Status of counter for calculated quantity at 8:00 - HI.
C8 Ai m3 Status of counter for calculated quantity at 8:00, calculated as C8 = 10000 * C8HI + C8LO.
VH Ai m3 Calculated quantity for the previous hour.
VD Ai m3 Calculated quantity for the previous day.

All values of current data ("P", "T", "F", "CLO", "CHI" and "C") are sent with the time stamp according to "ECSDTM" (i.e. time on conversion device when the last reading the current data) to the D2000 System kernel. A period of data reading is set according to the conversion device. For a device with mains power supply, it is about 10 minutes.

Time for RTU and conversion device is set remotely from a dispatching of SPP-Distribúcia a.s.


Archival data loading

The values of "VH", "CLO" , "CHI" and "C" can be read again from the so-called hour archive (max. 192 hour records).
The values of "VD", "C8LO", "C8HI" and "C8" can be read again from the so-called daily archive (max. 32 daily records).
Archival data can be loaded by Tell command GETOLDVAL with the parameters a station name and time from which you need these data.

Literature


  • Parallel data transmission from telemetry system of SPP-Distribúcia a.s. for wholesale gas customers, Revision 0.4, (c) SCT s.r.o. Košice, http://www.sct.sk.

Changes and modifications


-

Document revisions


  • Ver. 1.0 - 13. august 2010 - Creation of document
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