4.6.1 Protocol : Landis & Gyr - SCTM Communication


 

The transmission procedure is in accordance with the SCTM procedure ( coded serial tele-metering ) of the company Landis & Gyr. A "Conversational Information Transfer" similar ISO 2629-1973 resp. ECMA 29 is used that includes additionally an acknowledgement procedure with increased code security as well as the opportunity for multi point transmission. 

An ASCII  standard protocol is used with one start bit, 7 bits information, 1 parity bit and 1stop bit. The transmission of data bytes takes place after the principle "LSB first". It is an asynchronous protocol with hamming distance = 4. Each ASCII character is already secured with d = 2 over the parity bit in the asynchronous character. Both, header and data block are additionally secured with a checksum and therefore a hamming distance = 4 is reached for this section of the telegram. The HCC ( Header Check Code ) is calculated over the header exclusive SOH and inclusive data block length. The BCC ( Block Check Code ) is also a length parity character over the whole data block without header, calculated from the byte after the STX up to the ETX inclusive, according to ISO/1155-1978. 

 

Telegram structure

The telegram circulation is controlled by the master station ( ZS ) i.e. The RTU ( US ) replies only on inquiry. The analysis of the telegrams in monitoring direction is only possible in relation to the previously in control direction sent query. Therefore two channels corresponding with each other are used. One can select between channel 1 + 2 or 3 + 4. Recording in control direction ( Master -> RTU ) is done on channel 1 and recording in monitoring direction ( RTU -> Master ) on channel 2. The 2-channel recording has the advantage that RTU telegrams can be analyzed with the help of the previous master query.

Information about the structure of the telegrams see
<L&G SCTM : Telegram structure>

 


L&G SCTM : Configuration

 

 

With the channel button ( channel 1 ...12 ) on the bottom following settings are possible :

 

Each character has one start bit ( binary = 0 ), 7 information bits and normally one even parity bit and one stop bit ( binary = 1 ).

 

Interface

For each channel any COM port ( COM 1 till COM 24 ) can be selected.

Modem

An individual modem can be installed and connected for each channel. LIAN 98 is able to process up to twelve modems in the range of COM1 till COM24 simultaneously. Select here the modem assigned to the selected channel. Normally this assignment will be recognized by LIAN 98 and the corresponding modem will be set.

Setup Modem

The settings of the modem must be executed via the windows control panel "telephone and modem options". With this button you can check the modem settings and see if they correspond to the LIAN 98 configuration.

Connection type

Attention, the connection type should be set to full duplex for monitoring !
 

Full duplex :

Most of the modems are full duplex and can transmit data in both directions simultaneously. DTE ( LIAN 98 ) and DCE ( Modem ) work simultaneously as transmitter and receiver. None of both transmitters has to wait for clearance for transmitting data. Therefore the signals RTS and CTS are not significant. Sure, LIAN 98 is setting the control signals RTS and DTR to 1 when it is ready for transmission and receipt but it does not check the signals CTS and DSR.

Half duplex :

In case of a half duplex connection DTE ( LIAN 98 ) as well as DCE ( Modem ) can work as transmitter and receiver, hereby only one data line ( 2-wire connection ) is available that can be used alternately for transmission or receipt of data. The control signals RTS and CTS are used in order to define the allocation of transmission or receipt. When LIAN 98 should work as transmitter it activates the signal RTS and waits for the confirmation of the modem via the signal CTS. After the receipt of the signal CTS the data are transmitted and after the transmission of the data the signal RTS is set to 0. In each other case LIAN 98 is working as receiver only.

As long as the LIAN 98 software is ready for transmission and receipt the signal DTR is activated in order to show the modem that LIAN 98 is ready for operation, as well the software expects an activated DSR signal from the modem.

RTS Leading delay

0 ... 1000 msec
This parameter ist only used for the connection type "half duplex" and is determined by the initial transient behaviour of the used transmission equipment.
The RTS Leading defines the delay time from activating RTS signal to transmitting the first character and is used for modems whithout the hardware handshake signals "RTS and CTS". In this case the "RTS signal" must be led back over the "CTS line" to the PC with the help of a brazing bridge in the monitor cable. Dependent of the used modem it may be necessary to connect additionally the DTR-pin with the DSR-pin.
This function is deactivated if the "Leading and the Trailing" is set to NULL and therefore the control signals are analyzed diectly from the modem.

RTS Trailing delay

0 ... 1000 msec
This parameter ist only used for the connection type "half duplex" and is determined by the final transient behaviour of the used transmission equipment.
The RTS Trailing defines the delay time from the last character transmitted up to the RTS signal is deactivated.
This function is deactivated, if the "Leading and the Trailing" is set to NULL.

 

Baud rate

Transmission speed : 25 - 115200 baud ( variable )

Data byte

7 bit ( variable )

Stop bit

1 bit ( variable )

Parity

even ( variable )

Time out

1 - 9999 msec ( variable )

 

Settings in the channel window

 

 

Number of station fields

0, 3, 5 or  8

The station field consists by default of 3 numbers ( 000...999 ). Optionally station fields with 5 or 8 numbers are used. The station number can be omitted for US telegrams and/ or ZS telegrams whereby the lengths of the header is reduced. 
The length of the station field is a parameter defined by the system.

 


L&G SCTM : Simulation

 

L&G SCTM : RTI ( Master )-Simulation

 

 

 

L&G SCTM : RTU ( Slave )-Simulation

 

 

 

 


L&G SCTM : Pre-filter/ Pre-trigger

 

 

L&G SCTM : Monitoring filters

 

Monitoring filters reduce capture on particular pre-defined data records. By setting the corresponding filters a carefully directed data preselection can be achieved, which results in a reduction of the data to be analyzed later.

 

 

Filter released

yes / no

With this option already set monitoring filters for one channel can be deactivated temporarily without deleting them.

protocol specific
filter mask

Here monitoring can be filtered for telegram specific values in which several OR-linked filter masks can be defined for the channel.

= Only values equal to 'from' are let through.
# Only values not equal to 'from' are let through.
< Only values less than 'from' are let through.
> Only values greater than 'from' are let through.
r 'from' and 'till' define a valid range
add Adds the next OR-element.
remove Removes the current OR-element.

 

L&G SCTM : Action filters

 

For the simulation and execution of data tests actions can be caused with the receipt of defined records. Therefore the possibility exists to define action filters, that effect the transmission of a send-sequence or transmit one or more message buffers ( TDB ).

 

 

Action filter released

yes / no

With this option already set action filters for one channel can be deactivated temporarily without deleting them.

protocol specific
filter mask

The action filter is described over telegram specific features corresponding to a filter setting. Additionally each action filter requires an allocation to a send buffer or alternatively to a send sequence.

= Only values equal to 'from' are let through.
# Only values not equal to 'from' are let through.
< Only values less than 'from' are let through.
> Only values greater than 'from' are let through.
r 'from' and 'till' define a valid range
Sendbuffer number
( from, from/ till )

In correspondence with the action filter the message buffer "from" or the message buffers "from/ till" are to be sent.

Sequence line number
( from, from/ till )

In correspondence with the action filter the send sequence is to be started at line number "from" or to be started at line number "from" and to be ended at line number "till".

add Adds the next OR-element.
remove Removes the current OR-element.

 

L&G SCTM : Start trigger

 

With the receipt of a telegram pre-defined as start trigger, recording is started.

 

 

Start trigger released

yes / no

With this option already set start triggers for one channel can be deactivated temporarily without deleting them.

protocol specific
trigger mask

Here you can define telegram specific start triggers for monitoring in which several OR-linked triggers can be defined for the channel.

= Only values equal to 'from' are let through.
# Only values not equal to 'from' are let through.
< Only values less than 'from' are let through.
> Only values greater than 'from' are let through.
r 'from' and 'till' define a valid range
add Adds the next OR-element.
remove Removes the current OR-element.

 

L&G SCTM : Stop trigger

 

Monitoring can also be stopped by telegram-specific filters and/ or "stop on error" after a defined number of following records. The number of the following records is defined in the field "records after stop on error/ stop trigger" in the global parameters of the VFL settings.

 

 

Stop trigger released

yes / no

With this option already set stop triggers for one channel can be deactivated temporarily without deleting them.

protocol specific
trigger mask

Here you can define telegram specific stop triggers for monitoring in which several OR-linked triggers can be defined for the channel.

= Only values equal to 'from' are let through.
# Only values not equal to 'from' are let through.
< Only values less than 'from' are let through.
> Only values greater than 'from' are let through.
r 'from' and 'till' define a valid range
add Adds the next OR-element.
remove Removes the current OR-element.

 


Each alteration in the settings is displayed by an asterisk * in the caption title and will be only effective after saving.

 


L&G SCTM : Message display format

 

The sent and received messages of all channels are entered binary into the archive file. Before displaying on screen, the binary archived data are coverted to an easily readable procedure specific plaintext. In order to optimize the representation it can be chosen between three different plaintext settings. The plaintext format is set separately for each channel.
( see also "FMT file - Display format" )

 

 

Plaintext format 1

Everything is displayed : Telegram header and information element

Plaintext format 2, 3

No header is displayed : Only information element is displayed.

Plaintext format 4, 5

No information element is displayed : Only telegram header is displayed.

 

Additional to the plaintext output the transmission data can also be displayed in hexadecimal, decimal, ASCII, binary ( LSB first ) or binary ( MSB first ). Of course the plain text output can also be deactivated in order to display the transmission data only e.g. hexadecimal.


L&G SCTM : Error messages

 

Error checks during receive

 

per character

the start bit, the stop bit and the parity.

per frame

the start character, the frame checksum and the end character, the
length and second start character in frames with variable length.

 

*** TimeOut !

Within a telegram, there may be no pause between characters. In case of timeout occurs it is assumed that it is the end of the telegram and the telegram check is started. The sensitivity can be parameterized in the configuration ( timeout ).
Normally a time out is no error, but it is stored in the Pro file together with the initial error for a better analysis of the faulty transmission line in connection with a line error.

*E: COM-PORT !

Error during writing on the COM port. May be it is already occupied by another program.

*E: Length !

The stop byte ( 16H ) is missing or set wrongly.

*E: Format !

The repetition of the length or the start characters in the message header are faulty. For a fixed frame telegram, may be the parameter "Number of link address fields" is not set correct.

*E: Checksum !

The message checksum in the checksum byte is incorrect.

*E: SYNC !

The receive routine initially searches for 68H, 10H, E5H ( oder A2H ). Each other character is noted as synchronization error and inserted in the PRO file.

*E: Overflow !

Error message from the UART. This error is noted only in the PRO file.

*E: Parity !

Error message from the UART. This error is noted only in the PRO file.

*E: Start/ Stop !

Error message from the UART. This error is noted only in the PRO file.

 

Error checks during simulation

 

*E: DIR bit !

Direction bit ( Z/ U ) is set wrong.

*E: unexpected !

The respond at this time was not expected.

*E: Link address !

The received station number is incorrect or the entry in the SIM list is wrong.

 


L&G SCTM : Parameter list

 

The parameter list is not used for the Landis&Gyr SCTM protocol.

 


MAYR Software

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Manual LIAN 98


LIAN 98 Protocol Router, Simulator and Analyzer
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