Documentation

Enable

If enabled by the Show Enable port parameter, this port enables or disables the items defined in the Rules table. The signal connected to the port must be a boolean array whose length matches the number of defined rules. Each array element corresponds to a rule, following the order in the table; if no rule is defined, the port is hidden. A value of TRUE enables the corresponding rule, while a value of FALSE disables it.

Modifier

If enabled by the Show Modifier port parameter, this port sets the modifiers for the rules in message mode. The Modifier column in the Rules table no longer serves a purpose. The signal connected to the port must be a double array whose length matches the number of defined rules. Each array element corresponds to a rule, following the order in the table; if no rule is defined or the Mode parameter is not set to Message, the port is hidden.

This block does not have any output ports.

Server Station ID

Apply the Server Station ID of the corresponding Setup block. It must range between 0 and 65535.

Sample Time

Defines the base sample time at which this driver block gets its sample hit. This parameter can also be set to -1 for inherited sample time. The units are in seconds.

Mode

Specifies the basic operation of the block. In Peer mode, the block accepts or rejects connection attempts from specific remote clients. In Message mode, the block modifies the content of the message that will be sent to the client. In general, Modbus servers only send messages in response to client requests.

Rules

The table contains the action items for the Peer and Message modes. During runtime, the rules are processed sequentially from top to bottom. If the effects of multiple rules overlap, the last rule takes precedence. If rules are distributed across multiple Fault Insertion blocks, the execution order of those blocks also influences which rule takes precedence. Depending on the Mode parameter, the table displays different columns:

• Peer mode

  • The Action column defines how to handle incoming connection requests from clients. By default, if no rules are defined, all connection attempts from any client are accepted.

    Action	Description
    None	Disables the rule.
    Accept	Accepts the connection. Data transfer is allowed.
    Reject	Closes the connection. No data transfer is allowed.

  • The IP Address column defines the remote IP addresses to which the rule applies. Values can be scalars or two-element vectors, where the first element specifies the start of the range and the second element specifies the end of the range. Supported formats include character arrays such as '192.168.1.101', strings such as "192.168.1.101", string vectors such as ["192.168.1.101","192.168.1.105"], numeric scalars such as hex2dec('C0A80165'), numeric vectors such as [hex2dec('C0A80165'), hex2dec('C0A80169')], and cell arrays containing numeric values, strings, or character arrays such as {'192.168.1.101','192.168.1.105'}.

    If the value is -1, the rule is applied to all IP addresses.

  • The TCP Port column defines the remote TCP ports to which the rule is applied. Values must be numeric and can be scalars or two-element vectors, where the first element specifies the start of the range and the second element specifies the end of the range. Example of a single port: 502. Example of a port range: [500, 599].

    If the value is -1, the rule is applied to all ports.

• Message mode

  • The Action column defines how to manipulate the response message that is sent to the client. The action is processed only if the request message previously received from the client matches the filter criteria defined by the Unit, Function Code, and Index columns.

    Action	Description
    None	Disables the rule. The Modifier field is ignored.
    No response	No response is sent. The Modifier field is ignored.
    Trim response	The response message is shortened by a number of bytes defined by the modifier. The modifier must be in the range 0 to 65535. The Modbus header and its length field are not changed.
    Extend response	The response message is extended by a number of bytes defined by the modifier. The modifier must be in the range 0 to 65535. The Modbus header and its length field are not changed. The added bytes are filled with zeros.
    Send error code	The original response is blocked and a Modbus error message is sent instead. The error code is defined by the modifier, which must be in the range 0 to 255.
    Change transaction ID	Modifies the transaction ID of the response message. If the modifier is 0, the transaction ID is set to 0; otherwise, the modifier is added to the original transaction ID. The modifier must be in the range -65535 to 65535.
    Change length code	Modifies the length code, which specifies the length of the remaining message following the Modbus header. If the modifier is 0, the length code is set to 0; otherwise, the modifier is added to the original length code. The modifier must be in the range -65535 to 65535. The actual message length is not changed.
    Change unit	Modifies the unit value of the response message. If the modifier is 0, the unit is set to 0; otherwise, the modifier is added to the original unit value. The modifier must be in the range -255 to 255.
    Change function code	Replaces the function code in the response message with the modifier value. The modifier must be in the range 0 to 255.
    Change index	Modifies the index value of the response message. If the modifier is 0, the index is set to 0; otherwise, the modifier is added to the original index. The modifier must be in the range -65535 to 65535.
    Change quantity	Modifies the quantity value of the response message. If the modifier is 0, the quantity is set to 0; otherwise, the modifier is added to the original quantity. The modifier must be in the range -65535 to 65535. The actual message length is not changed.
    Change byte count	Modifies the byte count field, which specifies the overall number of bytes corresponding to the requested number of bits or registers. If the modifier is 0, the byte count is set to 0; otherwise, the modifier is added to the original byte count. The modifier must be in the range -255 to 255. The actual message length is not changed.

  • The Unit column defines a filter for the unit value in the request message received from the client. The rule is applied only if the received unit value falls within the specified range. Values can be numeric scalars or two-element vectors, where the first element specifies the start of the range and the second element specifies the end of the range. Valid values range from 0 to 255.

    If the value is -1, the unit value in the received message is ignored.

  • The Function Code column defines a filter for the function code value in the request message received from the client. The rule is applied only if the received function code falls within the specified range. Values can be numeric scalars or two-element vectors, where the first element specifies the start of the range and the second element specifies the end of the range. Valid values range from 0 to 255.

    If the value is -1, the function code value in the received message is ignored.

  • The Index column defines a filter for the index and quantity values in the request message received from the client. The rule is applied only if the requested data range overlaps with the specified range. Values can be numeric scalars or two-element vectors, where the first element specifies the start of the range and the second element specifies the end of the range. Valid values range from 0 to 65535.

    If the value is -1, the index and quantity values in the received message are ignored.

  • Depending on the selected action, the Modifier is either written directly to the corresponding field in the response message or added to the intended value of that field.

Show Enable port

If selected, the block shows the Enable input port; otherwise, the port is hidden.

Show Modifier port

If selected, the block shows the Modifier input port; otherwise, the port is hidden.