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Master Channel

The Master Channel configuration defines a "Scan Group" to a collection of field units that may be over one of the available serial or network circuits. The Master Channel defines how each field unit is scanned over the network, and is independent of which protocols are being used on individual field units.



Enter the Master Channel name.

This is the name which appears in the user diagnostics menu, and is also see in an HCP diagnostic window if used with Elecsys HCP. 

Channel Type

In some configurations this may be listed as "Direct Master", which includes a few operational differences noted below. The main differences between the Channel Types are listed below:

Direct Master

  • Global Scan Period
  • One failed poll changes RTU comms status.

Direct Master Flex Scan

  • Scan Period configured for each scan.
  • All "effective" polls must fail before RTU comms status fails. 
Auto Start

Select the automatic polling method for the channel.

Automatic polling types supported are:

  • Yes – polling started automatically upon power-up
  • No – polling started manually through the MMI
  • Link Based Poll – polling is started only after a P/R connection has been made from an HCP. 
Response Timeout

Enter the response timeout in milliseconds.

Time in milliseconds to wait for a poll response before declaring the message failed.

For Network Circuits, if a scan fails because the socket is broken or interface is unavailable, then the Master Channel protocol will wait a period of time (Response Timeout * 2) to try the next IP address in the Circuit. 

Broadcast Delay

Enter the broadcast delay in milliseconds. When a host computer sends a command to a field unit via the Master Channel, some field units do not want to be polled again for a certain amount of time to allow processing the command. This option allows normal polling to be delayed temporarily.

Delay in milliseconds after a command is sent to the field device before normal polling resumes. Normally this can be left to the default of 0. 

Interpoll delay

Enter the interpoll delay in milliseconds. Use this to add a delay between each poll sent by the channel to any field unit.

Time in milliseconds to wait between each poll. 

Scan Effective Limit

The Scan Effective Limit is the time (in seconds) defining which scans in the Scan Table are considered "effective" – meaning, polls which affect the status of the Field Unit if there are poll failures. Scan Table entries which have a Scan Period greater than the Scan Effective Limit do not mark the Field Unit offline when the scan fails.

For instance, if the Scan Effective Limit is configured for 30 seconds, then any scans defined with Scan Period <= 30 will be used to mark the Field unit online or offline. Scans with Scan Period greater than 30 will not mark the Field Unit offline even if they fail. The Scan Effective Limit only applies to the "Direct Master Flex Scan Table" version of the channel object.

A Scan Effective Limit of 0 disables this feature, thus all polls will affect the Field Unit status. 

Network Recovery

Enter the network recovery period in seconds.

Time period to wait after an RTU fails, before attempting to re-establish communications with that RTU. This will take the device off scan, allowing other devices on the channel to be polled more frequently and not waste as much time retrying a failed device. 

Scan Table

Click the Edit Table button to define the order and selection of polls to be sent to all field units on this channel, independent of protocol. Field Unit configurations (Modbus, etc.) define the protocol-specific nature of the individual polls that are sent.

Scan Table details:

Unit Address - This is the Field Unit Address as configured in each field unit on this Channel. (To force the Scan Table to ignore the Scan Period, enter a Scan Table row with the Unit Address of -1.) 

Poll Record - This is the row number in the Poll Record in the Field Unit definition. The first row in a Poll Table is referenced as record 1. Only those polls which are to be polled continuously need to be listed in this Scan Table. 

Scan Period - Enter the scan period in seconds. The Scan Period is the amount of time to use for scheduling each scan (global for all scans in the Direct Master, or configured per scan row in the Direct Master Flex Scan Table). 

For the Direct Master, the channel will restart the scan table sequence after the Scan Period has expired. If the total time for a given channel exceeds the scan period, the next scan shall be scheduled immediately.

For the Direct Master Flex Scan Table, each poll is scheduled based on its own Scan Period. If the total time required for scans at any point is greater than allowed by the Scan Periods, the scans will operate as fast as possible. 

Setting a Scan Period to a negative number will disable a scan. However, the first entry in the Scan Table for each Unit Address should not be disabled, or it may not correctly set the Alive/Dead status of the unit. 

Comment - Optional column, allowing a descriptive comment to be entered for each row in the table. The Comment field is unused in the configuration.

Async Circuit

An Async Circuit is a serial communications path to one or more field units from a common Master Channel, using an Async serial port. The Async Circuit allows for redundant serial ports to a common set of field units, such as a Primary and Secondary radio or modem communication path.


Primary Port

Select the primary physical communication port for this circuit. 

The selected port must be defined as an object under Networks, where its Async port properties (baud rate, etc.) are also defined (see the section 4-Master Channel section).

The same port (e.g. COM1) may also be shared with certain other tasks, such as Terminal Server, and may be used with Virtual Ports.


Network Circuit

A Network Circuit is an IP network communications path to one or more field units from a common Master Channel. The Network Circuit is used when the field unit is connected via a network, such as TCP/IP, PPP, or SLIP.


Circuit TypeSelect the circuit type as 'Network Circuit' 
Failover DelayTime to Live for network socket (in seconds). Make sure this is large enough to allow for the time it takes to poll on this circuit, taking into account timeouts and interpoll delays of all scans on the channel. 
Master Network  PortMust be consecutive, starting from 0 (unique among other types of circuits). 
The Network Circuit should have at least one Field Unit child object defined under it. 
Connect Table

Click the Edit Table button to edit the IP address or list of IP addresses to connect for the Field Unit(s) on this circuit. Entering multiple IP addresses will allow failover connections when one connection fails (all connections made to the same Master Network Port on different IP addresses). 

Destination Address Enter the IP address to connect.

The IP address must be in the same IP network or reachable via the Default Gateway or Route Table configuration.

Interface Enter the network interface over which to connect to this Destination Address. The network interface must match the Interface name in the ACE object (such as "Ether1") rather than the Linux interface name (such as "eth0").

DF1 RS-232 Async Circuit

The DF1 RS-232 Async Circuit is a special serial communications path to one or more Allen Bradley DF1 field units from a common Master Channel. Use this circuit instead of the generic Async Circuit when configuring a DF1 field unit under a Master Channel.

See the Protocol_DF1-CSP-Master protocol documentation for information on configuring the DF1 RS-232 Async Circuit and FieldUnit.

HART Circuit

The HART Circuit object is a special serial communications path for one or more HART devices from a common master channel. Use this circuit instead of the generic Async Circuit when configuring a HART device under a Master Channel.

See the Protocol_HART-Master protocol documentation for information on configuring the HART Circuit and FieldUnit.

NMEA (GPS) Field Unit


   The NMEA Field Unit object contains unique information for a special internal Field Unit that reads location information from an Elecsys cellular modem.


Unit Name

Enter the field unit name.

Unit name is displayed in diagnostic menus and in an HCP diagnostic screen.  

Unit Address

Enter the actual field unit address which is configured in the device being polled.

Valid Modbus addresses 1 to 255.

FieldUnit - Modbus Master (and others)

See the Elecsys documentation on various FieldUnit protocols for information on configuring the FieldUnit, including protocol-specific Poll Table, such as:


  – Protocol_HART-Master


RTDB – RealTime DataBase

  An RTDB (Real Time DataBase) defines the size of the virtual database reserved for the Field Unit. All FieldUnit objects require a child RTDB in order to function properly, which is defined using a numeric register address format (typically, using Modbus-like addresses).


The RTDB object supports several additional optional child objects (see the sections 4-Master Channel section 4-Master Channel sectionTag  Names4-Master Channel section, and 4-Master Channel section).

Database Definition

Click the Edit Table button to edit the details of the RTDB definition.

Point Count – Enter the number of data points of this type to be allocated space in the database.

Field Format – Select the point data format:

Boolean – Boolean
UINT8 – Unsigned 8-bit integer (0 to 255)
SINT16 – Signed 16-bit integer (-32,768 to 32,767)
UINT16 – Unsigned 16-bit integer (0 to 65,535)
SINT32 – Signed 32-bit long integer
UINT32 – Unsigned 32-bit long integer
REAL32 – IEEE floating point (32-bit)
STRING32 – Each field contains up to 32 ASCII characters
STRING256 – Each field contains up to 256 ASCII characters
EVENT – Timestamped event data obtained from field device.

The following field formats are the same as the above but do not generate an RBE flag when the data changes, even if the Field Unit is set to Produce RBEs=Yes.

No-Rbe Boolean – Boolean
No-Rbe UINT8 – Unsigned 8-bit integer (0 to 255)
No-Rbe SINT16 – Signed 16-bit integer (-32,768 to 32,767)
No-Rbe UINT16 – Unsigned 16-bit integer (0 to 65,535)
No-Rbe SINT32 – Signed 32-bit long integer
No-Rbe UINT32 – Unsigned 32-bit long integer
No-Rbe REAL32 – IEEE floating point (32-bit)
No-Rbe STRING32 – Each field contains up to 32 ASCII characters
No-Rbe STRING256 – Each field contains up to 256 ASCII characters

Data Address – Enter the address of the starting register within the RTDB for the Field Format and Count defined on this row.
The RTDB fields must be defined so they are non-overlapping, and there need to be enough data points defined to hold all of the data returned in the Poll Table entries defined for this FieldUnit.
All RTDB database fields (except String types) may hold 32-bit data items, regardless of the data type or address. The RTDB typically uses registers defined in the range of Modbus addresses, although this is not a strict requirement. However, if the RTDB is connected to a Modbus Slave Channel, it does require Modbus addressing to work properly as a slave (see the Modbus Slave Channel documentation).

Comment - Optional column, allowing a descriptive comment to be entered for each row in the table. The Comment field is unused in the configuration.



  A Deadband object defines deadbands for the data fields configured within a Real-time Database (RTDB). This is only used to reduce the communications traffic on an RBE (Report by Exception) connection. If no RBE connection is configured, an RTDB does not require a Deadband object.











Deadband for 30,001-30,004, 5% of its range





Deadband for 40,003





Deadband for 40,004


Pre-Initialized RTDB

  Ordinarily, all RTDB database locations are initialized to zero values upon system startup (or zero-length strings). However, sometimes it may be desired to initialize certain database locations to a non-zero value, before any polling or other data operation occurs. Each RTDB has an optional ACE object that allows one or more registers to be initialized at startup.


Init ValuesClick the Edit Table button to define any pre-initialized RTDB values. 
  • Data Address – Enter the starting register number to define default values. This should be a register number that is defined as part of the RTDB. 
  • Count – Enter a count of registers, beginning with Data Address, that should be initialized to the same value. 
  • Init Value – Enter the value to which the register(s) will be initialized on startup. For Boolean registers, enter a '0' or '1' initial value. For floating point registers, enter the initial value in floating point format. 
  • Comment - Optional column, allowing a descriptive comment to be entered for each row in the table. The Comment field is unused in the configuration.


Tag Names


RTDB database locations are configured using numeric address locations. However, the optional Tag Names child object under the RTDB allows one or more numeric address to be associated with an ASCII tag. This may be used for publishing data by tag using MQTT, for internal display using Custom Reports, and they may be used for other purposes.


Include Page
Tag Name Substitutions
Tag Name Substitutions

Data Blocking


The Data Blocking object allows groups of RTDB points to be blocked together for exception reporting (RBE) to an HCP. If any one point in the defined Data Block changes, all the points are reported, including the unchanged ones. If no data blocking capability is required, this object is optional.



Data Blocking does not work properly if you are using Pre-Initialized registers on the same RTDB. Blocks will be broken up at the boundaries of pre-initialized registers.

Data Blocking does not work if the blocks span discontiguous (non-sequential) register addresses in the RTDB.

Linux Timestamp

  A Timestamp object is used to store the time and date at which data is polled by a Master Channel. The timestamp is stored in register(s) within the RTDB, and thus may itself be reported with the RBE packet or polled via a Slave Channel. 
Timestamps may be stored in one of two conditions whenever a specified poll occurs: