Protocol : Landis & Gyr - SCTM Communication


 

The Landis & Gyr - SCTM Communication is also available in the LIAN 98 Software,
running under the operating system Microsoft® Windows® ( 32/ 64 bit ).

see : LIAN 98 Protocol Router, Simulator and Analyzer


 

The telegram circulation is controlled by the master station, i.e. the substation only replies on inquiry. The analysis of datablocks in monitoring direction is only possible concerning the command sent before in control direction.

 

L&G SCTM : Parameterization

 

 

CDE adapter

Switch setting PCM

Baud rate

100 - 19200 Baud ( variable )

Modulation mode

Asynchronous pulse code modulation

Data byte

7 bit ( variable )

Stop bit

1 / 2

Parity

even / odd ( variable )

Time out

250 msec ( variable )

Number of US bytes

0, 3, 5 and 8 ( variable )

 

SCTM : Telegram structure

 

SCTM telegrams are of variable length, but consist of at least one complete telegram header. All information bytes are in a 7 bit ASCII format.

 

There are header telegrams with four different lengths depending on the number of US-NO bytes.

  • Header length =  8, number of US-NO bytes = 0
  • Header length = 11, number of US-NO bytes = 3
  • Header length = 13, number of US-NO bytes = 5
  • Header length = 16, number of US-NO bytes = 8 ( US-NO + reflection )

The selection of the telegram header is a system parameter and is parameterized in LIAN DOS configuration.

 

Status byte

Control direction :
a , c , e , g  for US-NO = 0   or US-NO = 8
1 , 3 , 5 , 7   for US-NO = 3   or US-NO = 5
direction bit = 1 corresponds to ( Z ) control direction

Monitoring direction :
' ,  b , d , f   for US-No = 0    or US-No = 8
0 , 2 , 4 , 6   for US-No = 3    or US-No = 5
direction bit = 0 corresponds to ( U ) monitoring direction

Header Check Code

HCC is the length parity over all header bytes besides the SOH byte.

STX

STX indicates the begin of the datablock in the telegram.

ETX

ETX concludes the data section of the telegram. With a telegram without data section the header is concluded.

Block Check Code

BCC is the length parity over all datablock bytes, exclusive the control character STX and inclusive ETX.

 

IAC

The telegram type is identified at the one- or two digit IAC.
Possible values of IACs : E1 - E8, D/ P, I, N, S1 - S3, T1 - T4

 

In monitoring direction there is no possibility to identify the telegram type ( datablock ) without having the previously sent master command.

 

L&G SCTM : Transmission errors

 

*E:TimeOut !

Within a telegram, there may be no pause between characters. The sensitivity can be parameterized in the program LIAN DOS configuration.

*E:Overflow !

Error message from the UART.

*E:Parity !

Error message from the UART.

*E:Start/Stop !

Error message from the UART.

*E: StartOfHeader !

The receive routine initially searches for SOH. Every other character is given an asterisk ' * ' on the screen and a synchronization error is noted in the PRO file. ( SYNC error )

*E: DataBlockLength !

Length does not correspond to DBL bytes.

*E: HeaderCheckCode !

The header check sum in the HCC byte is incorrect.

*E: StartOfText !

The STX ( 02H ) is missing or set wrongly.

*E: BlockCheckCode !

The block check sum in the BCC byte is incorrect.

*E: EndOfText !

The ETX ( 03H ) is missing or set wrongly.

 


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Manual LIAN DOS


LIAN DOS Protocol Simulator and Analyzer
© Copyright 1991, 1996, 2001, 2006-2010 by Werner Mayr. All Rights reserved.