|Table of Contents|
The RediGate Configuration Manual describes the configuration of many of the RediGate's standard features using the ACE program. This document gives additional instructions for configuring the RediGate to use the following protocols:
HART Protocol Description
This document is not intended to provide a detailed description of the protocol(s) involved, nor to disclose proprietary information that may belong to other parties. Depending on the protocol, it may be necessary to refer to other vendor protocol documentation or device configuration details to understand how the RediGate should be configured to interface with it. This section provides a brief discussion of the protocol for the purpose of understanding the RediGate's configuration objects.
The Description and Enabled properties are included in ACE as part of each object but are not mentioned here. The "UFF External" property is only mentioned for the objects where it is typically used, but should normally be left unchecked.
HART Master Channel
The structure of ACE objects for a Master Channel used for HART protocol is shown below. Note the configuration must include the special HartCircuit and one or more HartCommand objects:
Note that a Scan Period of 0 milliseconds is (and also Response Timeout and Interpoll Delay of 0) is used to obtain the maximum HART scan rate, but actual communication delays are determined by built-in timing required by the HART protocol, which makes the effective scan rate about 2-3 polls per second. Any non-zero Scan Period will or Interpoll Delay will add additional poll delay beyond the timing required by the HART protocol, and a non-zero Response Timeout will increase delay on timeouts.
Although in the example above the Master Channel is only scanning for HART CMD 03 continuously, the other polls in the HART FieldUnit's Poll Table may be requested on demand using the device's Command Register (see RediGate-HART -MasterRTU Extra).
The HART Circuit object is a special 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.
|Circuit Type||Hart Circuit|
|Primary Port||Select the COM port that the HART modem is connected to|
|Reserved1||Reserved for future use|
|Reserved2||Reserved for future use|
Make sure to include an COM port (System → Networks → AsyncPort) object in the configuration with the instance number matching the physical COM port, and the baud rate corresponding to the field device’s setting. For a port connected to a HART modem device, the settings of the AsyncPort should typically be:
See the RediGate Configuration Manual for information on configuring the AsyncPort.
HART Field Unit
The FieldUnitHART object is used to configure polling of a particular HART device that is on a HART circuit.
|Poll Table Properties|
Select one of the HART Commands on each row of the Poll Table.
The list of HART Commands in this list is dynamic, depending on the ACE objects defined under HART Commands.
|Comment||The Comment column is an optional field, allowing a description to be entered for each row in the table. This is only for the user and has no effect on the operation of the RediGate.|
HART RTU Extra
The HART RTU Extra object
The Command Register is an integer register in the HART FieldUnit RTDB which is used to request the RediGate to send a HART command on demand.
To force a command in this device's Poll Table to be executed on demand, write into the Command Register the Poll Record row number of the poll to request. Note that the Command Register is the Poll Record number, not the actual HART command number. It is therefore recommended to configure the Poll Table for similar HART devices to be in an identical order, to avoid confusion over which Command Register value to use.
After a command is operated by writing to the Command Register, the resulting value in the Command Register indicates what was the result of the previous command, which may be read and acted on by a host system or internal RediGate logic.
The result values that appear in the Command Register are:
The Response Register is an integer register in the HART FieldUnit RTDB that will contain the two Command Status bytes included in each response from a HART device.
The least-significant byte (LSB) in the Response Register contains the Field Device Status (2nd byte of HART Status):
The next most-significant byte (MSB) in the Response Register contains the 1st byte of the HART Status. This is either a command-specific Response Code, or a communication or command response error.
|#Timeouts to Identify|
Enter the number of communication timeouts before the RediGate will revert to an Identity command to identify the HART device again.
This should typically be a low number (default is 5). The polling logic for the HART master protocol is:
The HART Commands object is a placeholder, under which one or more HART Command objects will be included.
|Parent(s)||System → Clients → Master Channels|
|Instance||Must be 0|
The HART Command object specficies a particular HART command and defines data types and RTDB registers in which to store the data used in communication with the HART device. HART Command objects are dynamically referenced by HART Field Unit Poll Tables. The name of the object is what is shown in the dropdown list of the Field Unit HART → Poll Table → Command Index column.
|Hart Command||HART command number as defined in the HART protocol (universal, common practice, or device-specific).|
This object defines the Data Type of fields associated with the particular HART command, and RTDB addresses in which to store the values returned from or sent to the device. Data fields must be included in this table in the order in which the bytes occur in the HART Data message.
If more Data bytes are received from a device than are referenced in this table, they are automatically discarded. Similarly, if the HART Command definition includes more bytes than are included in the actual HART message, command processing will cease when the bytes run out.
Data Type: Choose the correct datatype associated with the selected Action (Store, Discard, or Write) in order to parse bytes from the HART command message.
Action: Select one of three actions for processing bytes in HART command messages.
Read and Store: This action takes the response from the HART command and stores the data (whose type is defined by the selection in the "Data Type" column) in the RTDB address starting at the specified "Address" location.
Read and Discard: This action takes the response from the HART command and does not store it in any RTDB register (discards the bytes).
Write Data: This action is used for commands written to a HART device. Data is taken from the RTDB address starting at the specified "Address" location and builds an output message to the device according to the Data Type and Count. The values are sent in the order in which these "Write Data" entries are defined in the Definition Table for the command.
Count: Enter the number of sets of HART command Data to process according to the Data Type and Action specified.
Address: Enter a starting RTDB address register in which to store the bytes identified by Data Type format. For Write actions, the RediGate will use the current values in the registers to create the Data messages sent to the device. For Read and Discard actions, the Address field is unused but must be set to a value of at least 40001.
Comment: The Comment column is an optional field, allowing a description to be entered for each row in the table. This is only for the user and has no effect on the operation of the RediGate.
Examples of HART Command Definitions
The definition of a HART Command within the ACE configuration requires knowledge of the command structure (Data portion only), as published by the HART Communication Foundation or manufacturer device-specific command documentation. Several examples are given below.