Next, configure datasets in the Serial Device. Each Serial Device can have 16 datasets under it. Or you can have 16 devices with 1 dataset each. A dataset can be input or output. To add a new dataset, right mouse click on the Serial Device and select New Dataset. The following dialog will appear.
Configure the data direction to be input or output. In the above example, we are configuring an input dataset.
Next, click the DeltaV tab. The following dialog will appear:
In this dialog, configure the data type needed for DeltaV. You can see the available types by clicking on the drop down list. In the above example, we are configuring the input data type to be floating point.
Please see Section 4.1 for additional details for this parameter.
Next click the PLC tab. The following dialog will appear.
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In this dialog, we will map DeltaV data types to PLC (or external Device) data types. PLC data type values and corresponding PLC registers are:
Device Data Type Device Register
0 COILS
8 Dataset Scan Control
All other values Reserved
Table 4: PLC Data Type Values and Registers
The Start Address specifies where in the PLC to read the data. In this example, the starting address is 0.
This can be any PLC specific address. The starting address is specified as the offset, without the leading 1X, 3X or 4X. Maximum offset is 65535. The following table describes examples of PLC registers and corresponding start addresses in the dataset. The start address specified is actual offset address – 1.
PLC address Start Address Description
1 0 First coil in PLC. Start address is specified as 0.
1
501 500 Coil 501. Start address is specified as 500.
501
10123 123 Input Status 10123 or 100123. Offset 123 is the specified Start address.
100123
31000 999 Input Register 31000 or 31000. Offset 999 is the specified Start address.
301000
40001 0 First Holding Register. Start address is specified as 0.
400001
40950 949 Holding Register 40950 or 400950. Start address specified as offset 949.
400950
Table 5: PLC Registers, Start Addresses, and Descriptions
For floating point and 32-bit DeltaV datasets reading PLC tables holding data in bit registers, two 16-bit registers comprise a single value. The specified dataset Start address must be calculated accordingly.
In this example, the starting address is 0, the PLC data type is 3 and the maximum number of values is 50. This would result in the following DeltaV registers.
DeltaV Register PLC or External Device Registers
R1 0
Table 6: DeltaV and PLC Registers
In general, each dataset has a maximum of 100 16-bit values of DeltaV data type (as configured in the previous dialog). Each DeltaV value is mapped to one or more PLC registers. If two registers are required, as is the case for floating point values, the registers must be consecutive. The following table describes the mapping:
DeltaV Data Type PLC Register Type PLC Registers Required Max Number of Values
Signed 8 bit Integer Coils Input Status
1 – Bit or Byte 100 Signed 16 bit Integer Coils
Input Status Input Registers Holding Registers
1 - 16 bit word 100
Signed 32 bit Integer Input Registers Holding Registers
2 - 16 bit words 50 Unsigned 8 bit Integer Coils
Input Status
1 - 16 bit word 100 Unsigned 16 bit Integer Coils
Input Status Input Registers Holding Registers
1 - 16 bit word 100
Unsigned 32 bit Integer Input Registers Holding Registers
2 - 16 bit word 50
Floating Point Input Registers Holding Registers
2 - 16 bit word 50
String Holding Registers 1 byte 100
Table 7a: Dataset Specification
PLC Register Type Modbus Function Code
Coils FC 1
Input Status FC 2
Input Registers FC 4 Holding Registers FC 3
Table 7b: Modbus Read Function Codes
PLC Register Type Output Dataset with Output Mode Value
Table 7c: Modbus Write Function Codes
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Lastly, for each dataset click on the Special data tab. The following dialog will appear:
Special data 1 value is used when transferring data for Floating point, signed 32-bit integer and unsigned 32-bit integer registers. Special data 2 is used to indicate the number of registers used for Floating point and 32-bit integer values. Details of Special data usage are provided in the Customization section 5.7.
Next, configure an output dataset in the Serial Device. The following dialog will appear.
Configure the data direction to be output. Select the Output mode. Output mode of 0 indicates Block outputs, i.e., the entire dataset is written out to the PLC if any dataset register changes. An Output mode of 1 indicates Single value output, i.e., only the value that has changed will be written out. See Table 7c above for Modbus function codes used.
Output datasets can also be read back from the PLC by selecting the Output readback checkbox. Note that for Output datasets with readback, pending output changes always have precedence over field reads. However, after serial card download from the controller, the VIM provides a special data flag to force a field read prior to allowing the DeltaV controller to send a write. By using this flag, the controller will first receive the data contained in the field device, followed by any subsequent DeltaV control actions.
Refer to Section 5.7 for additional details regarding this Read Before Write functionality.
The port level Send Outputs on Startup parameter affects writes to external devices as described below.
Simplex VIM – Send Outputs on Startup checkbox is Checked:
1. After VIM reboot (the controller automatically downloads the VIM serial cards), the default dataset values are written into the runtime database, and also written to the external device.
2. On card download, if dataset parameter changes are detected, i.e., number of values, start address, etc., have changed, the default dataset values are written into the runtime database, and the VIM also writes these values to the external device. Thereafter, all writes are on change of state driven by the DeltaV controller.
3. On card download, if no dataset parameter change is detected, the default dataset/register values are ignored. Instead, the VIM writes the current dataset values for all output datasets to the external device. All other writes are driven by the DeltaV controller on change of state.
Simplex VIM – Send Outputs on Startup checkbox is Unchecked:
1. After VIM reboot (the controller automatically downloads the VIM serial cards), the default dataset values are written into the runtime database, but are not written to the external device.
2. On card download, if dataset parameter changes are detected, i.e., number of values, start address, etc., have changed, the default dataset values are written into the runtime database. If no dataset parameter changes are detected, the default data values are ignored.
3. All other writes are driven by the DeltaV controller on change of state.
Redundant VIM – Send Outputs on Startup checkbox is Checked:
1. After VIM reboot (the controller automatically downloads the VIM serial cards), the default dataset values are written into the runtime database, and also written to the external device.
2. On card download, if dataset parameter changes are detected, i.e., number of values, start address, etc., have changed, the default dataset values are written into the runtime database, and the VIM also writes these values to the external device. Thereafter, all writes are on change of state driven by the DeltaV controller.
3. On card download, if no dataset parameter change is detected, the default dataset values are ignored. Instead, the VIM writes the current dataset values to the external device.
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4. On VIM switchover, the current values are written to the external device.
5. All other writes to the external device are driven by DeltaV controller on change of state.
Redundant VIM – Send Outputs on Startup checkbox is Unchecked:
1. After VIM reboot (the controller automatically downloads the VIM serial cards), the default dataset values are written into the runtime database, but are not written to the external device.
2. On card download, if dataset parameter changes are detected, i.e., number of values, start address, etc., have changed, the default dataset values are written into the runtime database. If no dataset parameter change is detected, the default data values are ignored.
3. On VIM switchover, the current values are written to the external device.
4. All other writes to the external device are driven by DeltaV controller on change of state.
Next, click the DeltaV tab and select DeltaV data type as floating point.
Next, click the PLC tab. The following dialog will appear.
Note that the Data start address is now 100. This is because in our example, the first dataset has 50 floating-point values. Consequently, this dataset starts at R101.
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