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Dataset Special Data Tab

The special data parameters of a dataset contain the target PLC Data File number and other advanced communication flags.

Special Data 1

PLC-5 /SLC File Type (PLC5/SLC Messaging Mode)

For ControlLogix devices, you must map internal native tags to PLC5/SLC file types and file numbers when using DF1 DeviceDataTypes. When using Generic ENBT communications (DeviceDataType=15), special data values are not used.

0 = Output File Type, O

1 = Input File Type, I

2 = Status File Type, S

3 = Binary File Type, B (16-bit aligned access)

4 = Timer File Type, T (Configuration Details)

5 = Counter File Type, C (Configuration Details)

6 = Control File Type, R (Configuration Details)

7= Integer File Type, N

8 = Floating File Type, F

9 = ASCII File Type, A (Configuration Details)

10 = String File Type, ST (Configuration Details)

13 = Binary File Type, B (32-bit aligned access for ControlLogix v16)

14 = Long File Type, L (32-bit Integer access for MicroLogix and ControlLogix)

Special Data 2

PLC-5 /SLC File Number (PLC5/SLC Messaging Mode)

0 – 65535 file number

For example, when reading/writing Integer file N15, configure special data 1 as 7, and special data 2 as 15. Similarly, when reading/writing Floating point file 8, configure special data 1 as 8 and special data 2 as 8.

Special Data 3

Dataset-Level Transmit Delay

If this value is non-zero, a delay is added between input scan messages of this dataset. The delay is equal to the value of this parameter times 10 ms.

Dataset Transmit Delay = Special_Data_3 * 10 ms

Special Data 4

Logix CPU Slot Number

  • For Logix, this parameter is configured such that the low byte is always set to 1, and the high byte is the Logix CPU slot number in the chassis. The slot number is zero based. For example, if the CPU is in the first slot (slot 0), configure a 1 for this parameter. If the CPU is in second slot, configure a 257 for this parameter. The parameter is calculated as (256 X slot) + 1.

  • For SLC 505 and PLC5/XXe, this parameter should be set to 0.

  • For CompactLogix, set this value to 1. The CPU in a CompactLogix is always in Slot 0.

Special Data 5

Special Communications Flags

See Table 2 below for more details. To calculate the correct value for this parameter, add all of the bit values for the flags that need to be enabled.

Table 1 - Special Data Parameters

Special Communications Flags
Bit Value Option Name Description
1 First Pass Read Before Output

In simplex mode, if a dataset is configured as Output with Readback, then as part of VIM initialization (after reboot or download from DeltaV controller), the dataset is read by the controller in order to synchronize the controller tables. However, at that time, the VIM has not completed its read of the field. Consequently, the data read back into the controller is all zero. Upon read completion, the controller proceeds to perform its normal write cycle, thus writing zero values back to the VIM.

In the VIM, since Output commands have the highest priority, these zero values are immediately written to the field, prior to any reads being performed. This leads to loss of any data which might be present in the PLC table being written. For any dataset configured as Output with Readback, enable this flag to prevent the above behavior.

This flag indicates to the VIM that on first pass, all outputs to this dataset are discarded until the PLC table has been read. On read completion, the field data is sent to the DeltaV controller and then normal output command priority is resumed.

If this flag is disabled, then normal default output command priority is always in effect, i.e., no first pass field read will be performed. This flag is dataset specific: first pass read is only performed on the dataset with this flag enabled. Other datasets continue to work with their default output command priority.

2 Use PLC Device ID

Includes the Device Address in the EtherNet/IP message.

This flag is used when communicating through an EtherNet/IP gateway device, such as an EtherNet/IP to DH+ gateway. In this scenario, the IP address defined for the device is the address of the bridge used to access the desired field device.

If this flag is disabled, the devcie address is not included in the EtherNet/IP message to the field device.

Table 2 - Special Communications Flags