General
The Allen-Bradley CompactLogix PLC uses MSG function blocks to create the Client interface for initiating the EIP PCCC transfers. For Write messages, the MSG function block specifies the source location of the data to be sent to the appropriate dw210 addresses. For Read messages, the MSG function block specifies the destination for the data when a range of dw210 addresses is queried.
For the following PLC programming example, the previously described drive.web Configuration with eight contiguous parameters mapping to PLC addresses N27:0-7 (Writes) and N29:0-7 (Reads) is used.
For the CompactLogix PLC, two MSG blocks must be instantiated in the program. One for writing the data to the dw210 and another for reading the data. There will be a different Message Control block for the read and the write transfers of data.
Write MSG Block
The Write MSG block's configuration information is stored in dwblock02_msg_ctrl Message File as shown below:
Message Configuration
Clicking on the small gray button to the right of the dwblock02_msg_ctrl name opens a Message Configuration window. Select the Configuration tab.
Configuration Tab
Refers to the MSG function block's interaction with the local CompactLogix processor.
| Message Type: | PLC5 Typed Write | Type of EIP PCCC command. |
| Source Element: | dwblock02_data[0] | Local PLC starting address of the write data. |
| Number Of Elements: | 8 | Number of 16-bit parameters to write. |
| Destination Element: | N27:0 | Starting address in the dw210 of the write data. |
Communications Tab
The Communications tab is used to set the destination address of the EIP PCCC Server, in this case, a dw210.
| Path: | LocalENB | Name of the Ethernet module in the local PLC. |
| 2 | Port number for the Ethernet port in local PLC. | |
| 192.168.1.71 | IP address of the dw210. | |
| Communication Method: | CIP | Route the message through the Ethernet network. cia the Control and Information Protocol (CIP). |
Tag Tab
The Tag tab associates the MSG block with the appropriate Message Control block.
| Name: | dwblock02_msg_ctrl | Storage location for all the Message Control parameters. |
Read MSG Block
The Read MSG block's configuration information is stored in dwblock01_msg_ctrl Message File as shown below:
Message Configuration
Clicking on the small gray button to the right of the dwblock01_msg_ctrl name opens a Message Configuration window. Select the Configuration tab.
Configuration Tab
Refers to the MSG function block's interaction with the local CompactLogix processor.
| Message Type: | PLC5 Typed Read | Type of EIP PCCC command. |
| Source Element: | N29:0 | Starting address in the dw210 of the read data. |
| Number Of Elements: | 8 | Number of 16-bit parameters to write. |
| Destination Element: | dwblock01_data[0] | Local PLC starting address of the read data. |
Communications Tab
The Communications tab is used to set the destination address of the EIP PCCC Server, in this case, a dw210.
| Path: | LocalENB | Name of the Ethernet module in the local PLC. |
| 2 | Port number for the Ethernet port in local PLC. | |
| 192.168.1.71 | IP address of the dw210. | |
| Communication Method: | CIP | Route the message through the Ethernet network. cia the Control and Information Protocol (CIP). |
Tag Tab
The Tag tab associates the MSG block with the appropriate Message Control block.
| Name: | dwblock01_msg_ctrl | Storage location for all the Message Control parameters. |
Sample Program
The preceding sections only cover the basic MSG block's configuration. A sample program with detailed triggering, error recovery, and comms link performance indicators are included in a complete sample CompactLogix program available at driveweb.com. A savvy-ready complementary loopback dw210 configuration is included in this download.
Click here to download the sample program.