Rockwell Automation 20-750-DNET PowerFlex DeviceNet Option Module - Manual (Page 73)

Rockwell Automation Publication 750COM-UM002B-EN-P - October 2012 73
Using Explicit Messaging Chapter 6
ControlLogix – Formatting a Message to Read Multiple Parameters
Figure 18 - Scattered Read Message Configuration Dialog Boxes
The following table identifies the data that is required in each box to configure a
message to read multiple parameters.
Configuration Tab Example Value Description
Message Type
Service Type
(1)
Service Code
(1)
Class
Instance
Attribute
Source Element
Source Length
Destination
CIP Generic
Custom
4d (Hex.)
93 or 9F (Hex.)
(3)
0 (Dec.)
0 (Hex.)
Scattered_Read_Request
(4)
40 bytes (4)
Scattered_Read_Response
(5)
Used to access the DPI Parameter Object in the option module.
Required for scattered messages.
Code for the requested service.
Class ID for the DPI Parameter Object.
Required for scattered messages.
Required for scattered messages.
Name of the tag for any service data to be sent from scanner to the option module/drive.
Number of bytes of service data to be sent in the message.
The tag where the data that is read is stored.
Communication Tab Example Value Description
Path (2) My_DeviceNet_Scanner The path is the route that the message will follow.
Tag Tab Example Value Description
Name Scattered_Read_Message The name for the message.
(1) The default setting for Service Type is ‘Custom’, enabling entry of a Service Code not available from the Service Type pull-down menu. When choosing a Service Type other than ‘Custom’ from the
pull-down menu, an appropriate Hex. value is automatically assigned to the Service Code box which is dimmed (unavailable). When reading 32-bit REAL (floating point) parameters, as in this
example, data conversion using COP (Copy) instructions or UDDTs is required to correctly show the parameter values.
(2) Click Browse to find the path, or type in the name of the device listed in the I/O Configuration folder (for this example, My_DeviceNet_Scanner). Then always type in a comma followed by a ‘2’
which is the DeviceNet scanner port, followed by another comma, and then the node of the drive (for this example, ‘1’).
(3) See Table 4 on page 66 for limitations of PowerFlex 750-Series drives when using DPI Parameter Object Class code 0x93 or Host DPI Parameter Object Class code 0x9F for explicit messaging.
(4) In this example, we are reading five 32-bit REAL (floating point) parameters. Each parameter being read requires two contiguous DINT registers. Therefore, a controller tag was created with its
Data Type field set to ‘DINT[10]’. Also, the Source Length field on the Message Configuration dialog box must correspond to the selected Data Type in bytes (for this example, 40 bytes for a
DINT[10] array). Scattered read messages always assume that every parameter being read is a 32-bit parameter, regardless of its actual size. Maximum message length is 128 bytes which can
read up to 16 parameters, regardless of their size. For parameter numbering, see
DPI Parameter Object on page 109 (Class code 0x93) or Host DPI Parameter Object on page 123 (Class code 0x9F).
(5) The controller tag for ‘Scattered_Read_Response’ must be the same size as the controller tag for ‘Scattered_Read_Request’ (for this example, 40 bytes), but can be a different data type (for this
example, a UDDT to handle conversion to parameter values that are a REAL data type).