In master mode, the Serial Card exchanges data with the serial device through a dataset. A dataset is a collection of parameters associated with a serial device. The parameters in the dataset hold data values that correspond to registers or data in a serial device.
The dataset defines the type and amount of data being sent to or received from the serial device. All the data values for a dataset have the same properties. Properties include the data type, data direction, and so on. The data values in a dataset map to a contiguous series of serial device registers or data.
In slave mode, the Serial Card emulates sets of data through datasets. The datasets are used to define the data that the Serial Card and DeltaV system are to emulate. The dataset in the slave mode defines the type and amount of data the Serial Card supports. All the data values for a dataset have the same properties.
You can create as many as 16 datasets for each Serial Card port. These 16 datasets can be allocated to the serial devices in several ways. For example, you can configure one serial device with 16 datasets, or you can have 16 devices on the port with one dataset each.
The DeltaV Explorer help describes how to add a dataset for a Serial Card. Basically, you define the dataset through the Serial Dataset Properties dialog. The following table defines the fields in the dialog.
Property |
Card Type |
Valid Values |
Description |
|---|---|---|---|
Data direction |
Standard, Programmable |
Input or output |
Defines whether this dataset sends DeltaV data to a serial device (output) or receives data from a serial device (input). The Data Direction indicates whether this data set is input data from the slave device or output data to be sent to the slave device when in master mode. The Data Direction is not needed when in the slave mode. The default value for Data Direction is Input. |
Dataset Tag |
Standard, Programmable |
An existing Dataset Tag or a new Dataset Tag you create by typing in a name. |
Identifies the Dataset Tag associated with this dataset. You use the Dataset Tag when configuring a module that reads from or writes to a serial device. |
DeltaV data type |
Standard, Programmable |
Boolean; discrete; 8-bit, 16-bit, and 32-bit signed integers; 8-bit, 16-bit, and 32-bit unsigned integers; floating point; and string |
Determines the type of data this dataset contains (Boolean, discrete, integer, floating point, and so on). This field value creates storage space for the dataset and determines how the DeltaV System accesses the data. The String data type is only valid if the PLC data type is input registers or holding registers. |
DeltaV start address |
Programmable |
0 to 65535 |
Indicates to which device address this dataset corresponds. |
Description |
Standard, Programmable |
As many as 256 characters |
Describes the use of the dataset. This description only appears when you view the properties of the dataset from the DeltaV Explorer. |
Number of values |
Standard, Programmable |
Standard cards: dependent on the PLC data type and the DeltaV data type. Refer to the table entitled Maximum Number of Values for Datasets for details. Programmable cards: 0 to 100. |
Standard cards: the number of Modbus values (registers or coils) to be read or written when in master mode. When in slave mode, the Number of Values defines the size (in registers or coils) of the data set used to emulate Modbus data. Programmable cards: the number of data values to be read from or written to the custom device. |
Output mode |
Standard, Programmable |
Complete block or single value |
The Output Mode controls how output data is transmitted to the Modbus slave when the Serial Card is in master mode. If the Output Mode is set to Block, then the entire data set is output when any value in that set changes. If the Output Mode is set to Single Value, then the outputs are set to the Modbus device one value (register or coil) at a time when the values are changed. The Output Mode is only configurable if the Data Direction is set to output. The default value for the Output Mode is Block. |
Output read back |
Standard, Programmable |
Checked or unchecked |
Determines whether the output dataset should be read back during the Serial Card's input scan. If this box is checked, the Serial Card reads back the values during the card's next input scan. The values that are read back update the current output values. If this box is not checked, no output read back will be performed. You can only configure this field if the Data direction is set to output. This field is not applicable when in slave mode. |
PLC data type |
Standard |
For outputs: coils or registers For inputs: coils, input status, input registers, holding registers, diagnostic data For slave mode: coils, input status, input registers, or Holding Registers |
For master mode, defines which data table to read from or write to in the serial device. For slave mode, defines which data table (type) the Serial Card is to emulate. |
PLC register offset |
Standard |
An integer from 0 to 9999 |
Identifies the starting register that maps to the first dataset parameter. |
PLC start register address |
Standard |
Read only |
Indicates the PLC register address corresponding to the first value in the Modbus device or configured data type. |
Special Data |
Programmable |
0 to 65535 |
Special Data fields can be used for any purpose not covered by the standard fields. |
For example, the user needs a dataset with the following parameter values:
Output mode: Output
DeltaV datatype: floating point
PLC datatype: holding registers
Number of values: 2
The following steps describe how to configure the values:
Right-click the device (for example, Dev01 under port PO1).
Select New Dataset.
On the General tab, select output in the Data direction field.
On DeltaV tab, select Floating point with status in the DeltaV data type field.
On the PLC tab, select holding registers and set Number of values to 2.