MICROTEL 700 communication protocol

Supported device types and versions
Communication line configuration
Communication station configuration
Alternative communication path
I/O tag configuration
Redundant system
Errors and problems
Details of the protocol implementation
Tell commands
Literature
Changes and modifications
Document revisions

Supported device types and versions

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Communication line configuration

• Category of communication line: Serial, SerialOverUDP Device Redundant, RFC2217 Client, TCP/IP-UDP
• Parameters of the serial line according to the setting of the telemetric system.
• UDP Parameters:
  • The parameters of a primary server or a secondary one (or parameters of primary/secondary network interface in case of a server with multiple network interfaces) are mandatory.
  • Host: string max. 80 characters – a server name in the INET form (the name or numerical address a.b.c.d).
  • Port: UDP port number (1 to 65535).

Global parameters:

Communication station configuration

• Communication protocol: Microtel 700.
• The station address is a number within the range 1 to 253. Do not use the addresses 0, 254, and 255. They are filtered because they often occur at the beginning of response (error in transmission system).

Parameters of station protocol

Dialog window of station configuration - the "Protocol parameters" tab.

Table 1

Alternative communication path

With help of protocol parameters, you can configure a so-called alternative communication path for the particular station (only for SerialOverUDP Device Redundant and TCP/IP-UDP lines). If the communication via the standard path fails, the availability of communication via the alternative path (when configured) is tested. The communication via the alternative path uses UDP packets that are identical to packets used in SerialOverUDP Device Redundant line. The usage of the alternative path is signalized by the FLB flag and a combination of FLN, FLO, FLP flags in the station value.

I/O tag configuration

Possible I/O tag: Ai, Ao, Ci, Co, Di, Do, Qi.

The I/O tags of Ci and Co type are not used for a usual operation but only for service purposes. They display and record the values of modules in a raw form without the conversion to a physical value. The values of modules are 16-bit, thus a numerical in the range of 0 to 65535.

The structure of I/O tag address:

• All types of values require the setting of the basic address, the so-called module, which is the number in the range of 0 to 63.
• Set the bit number in the range of 0 to 15 for Di, Do, and 0 to 14 for Qi.
• For Ai and Ao type values - insert data for conversion of a raw form to the physical value, so-called "RTU table index", and minimum/maximum of physical value. RTU table index defines the range of raw values which is used in the next recalculation (see Table 2). 

Table 2

The conversion of Ai inputs from the raw values "Raw_Value" to the physical value (Physical_VALUE) is done according to this formula:

Scale = (Physical_MAX - Physical_MIN) / (RTU_MAX - RTU_MIN)

Offset = ((Physical_MIN * RTU_MAX) - (Physical_MAX * RTU_MIN)) / (RTU_MAX - RTU_MIN)

Physical_VALUE = (Raw_Value * Scale) + Offset

The conversion of Ao outputs from the physical value to the raw one is done by the inverse function:

Raw_Value = (Physical_VALUE - Offset) / Scale

The calculation of value "Scale" is modified to 0 (zero) so the recorded value is 0. This situation occurs if a user configures the physical minimum the same as the maximum.

I/O tags of Qi type may use a special setting for the conversion of a 2-bit input value to a required status value. The implicit conversion is stated in Table 3.

Table 3

Redundant system

This protocol supports two modes of activity:

1. The connection to the "hot" server (HS). The protocol executes the active communication by sending the request for data according to configuration. 
2. The connection to the "standby" server (SBS). The protocol just reads and analyzes the received data. To get the line and all the stations to this status at any time, you can activate the SCAN protocol parameter in the configuration of at least one station.

The change from SBS -> SS is done with a transient phase. It means that data are read during one minute to detect inactivity on the communication line and whether the previous D2000 KOM, connected to the HS server, has changed to mode 2 (SBS).

Errors and problems

The error messages, mentioned below, may occur during the startup or during communication. It is recommended to activate the monitoring of communication in the configuration of lines for easier identification of problems. You can choose it from these levels:

• Monitor (at least)
• Monitor & Disk (recommended)
• Disk (recommended)

When you set "Monitor & Disk" or "Disk", the line_name.LOG file will be created in the Trace subdirectory in the application directory on the computer with the running communication process. This file contains all the debug and error messages.

Errors in the passive phase of communication

The D2000 KOM process connected to the SBS server could display the following error messages:

Details of the protocol implementation

Supported and used functions: 

COMMAND 3 - Change of State Scanning

Scanning of the changes in the block of modules since the last data reading. This function is not used after starting the communication (all the values are unknown) and for the reading which comes after the communication error. In these situations, the value of all configured I/O tags is read.

COMMAND 2 - Data Streaming

The value reading of the modules. It optimizes the reading of the configured (configured only!) adjacent modules en bloc until completing of MODULE_CNT by one datagram.

COMMAND 7 - High Security Relay

The writing of the new value for binary I/O tag of Do type. It is executed in two phases.

COMMAND 4 - General Purpose Output

The writing of the new value for I/O tags of Co or Ao type.

Tell commands

Literature

• MICROTEL 700 Telemetry.

Changes and modifications

• January 9, 2008 - Alternative communication path.
• September 19, 2017 - Multiple hosts can be entered in the alternative communication paths, TCI/IP-UDP line is supported.

Document revisions

• Ver. 1.0 - September 2, 2003 - Document created
• Ver. 1.1 - January 9, 2008 - Document updated
• Ver. 1.2 - September 19, 2017 - Document updated