Configure the Modbus Scanners Settings
The Modbus tab on the Forms of SCADAPack x70 Modbus Point Scanners includes a Modbus Scanners section. Use the section to configure how the SCADAPack x70 reads and writes with points associated with the Modbus Slave device.
Operation
Use this combo box to specify whether the SCADAPack x70 reads from, or writes to, the point on the Modbus Slave device. Select from Read (the default setting), Write, or Read/Write. The options that are available vary, depending on the Modbus Data Type that is specified in the Configuration section of the tab (see Configure the Modbus Point Scanner Configuration). The Write option is not available for counter data types.
Ensure that the Operation is set to Read if the Modbus Point Scanner is to read counter data. (As the SCADAPack x70 device does not write to counters.). When the Operation field is set to Read, the rest of the fields in the Modbus Scanners section are disabled.
If writing to DINT, Real or UDINT data types, the Write Holding Registers setting must be set to Multiple (Function Code 16). The options define the type of data to which the Scanner can write (see Configure the Modbus Point Scanner Configuration).
Write Outputs
This combo box is only available for use when the Operation is set to Write or Read/Write. Use this combo box to specify when the SCADAPack x70 writes to the point on the Modbus Slave device. Choose from the following:
At Scan Rate
Write to the point at the Default Scan Rate configured for Slave device, see Configuring a Modbus Slave Device or at the Scan Rate defined on this form (see Scan Rate below). This option is enabled only when the Operation field is set to Write.
This is the default setting when the Operation field is set to Write.
On Change
Write to the point when the point value changes. This option is available when the Operation field is set to Write or Read/Write.
This is the default setting when the Operation field is set to Read/Write.
At Scan Rate and On Change
Write to the point at both the Default Scan Rate configured for the slave device, and when the point value changes (see Configuring a DNP3 SCADAPack E Modbus Slave Device ). This option is enabled only when the Operation field is set to Write.
This combo box is only available when the Operation field is set to Read/Write. Use this combo box to specify the operation the SCADAPack x70 should perform while the point is offline. Choose from the following:
Send Read Requests
Send read requests to the Slave or Server at the scan rate specified for the device, or at the scan rate specified for the point scanner if that scan rate is different than the device scan rate.
This is the default setting.
Send Write Requests
Send write requests to the Slave or Server after a change in value or after a write command from another source.
If a write request is sent while a read request is still in progress, the value of database objects that are part of both requests is not updated.
If a write request is sent while there are buffered read requests for that point scanner, the buffered read requests are canceled. If a read request is in progress, it continues.
This combo box is only available when the Operation field is set to Read/Write. Use this combo box to specify the operation that should occur when a write failure occurs. Choose from the following:
Revert Point Values
Return database objects to their previous value when the write operation is unsuccessful.
This is the default setting.
Retain Point Values
Keep the current values for database objects when the write operation is unsuccessful.