Configuring the CONTROL and DATABUF Parameters

Overview

The CONTROL and DATABUF output parameters define the operation performed by the MBP_MSTR function block. For the EtherNet/IP protocol, the structure of the CONTROL and DATABUF output parameters remains the same for every explicit messaging service.

Configuring the Control Parameter

The Control parameter consists of 9 contiguous words, as described below:

Register	Function	Description
CONTROL[0]	Operation	14 = unconnected 270 = connected
CONTROL[1]	Detected error status	Holds the event code (read-only).
CONTROL[2]	Data buffer length	Data buffer length, in words
CONTROL[3]	Response offset	Offset for the beginning of the response in the data buffer, in 16-bit words Note: To avoid overwriting the request, confirm that the response offset value is greater than the request length CONTROL[7].
CONTROL[4]	Slot	High byte = slot location on backplane
CONTROL[4]	Slot	Low byte = 0 (not used)
CONTROL[5]1	IP address	High byte = byte 4 of the IP address (MSB)
CONTROL[5]1		Low byte = byte 3 of the IP address
CONTROL[6]1		High byte = byte 2 of the IP address
CONTROL[6]1		Low byte = byte 1 of the IP address (LSB)
CONTROL[7]	Request length	Length of the CIP request, in bytes
CONTROL[8]	Response length	Length of the response received, in bytes Read only—set after completion
1. For example, the Control parameter handles the IP address 192.168.1.6 in the following order: Byte 4 = 192, Byte 3 = 168, Byte 2 = 1, Byte 1 = 6.

Configuring the Data Buffer

The data buffer varies in size. It consists of contiguous registers that include—in sequence—both the CIP request and the CIP response. To avoid overwriting the request, confirm that the data buffer is large enough to simultaneously contain both the request and response data.

Data Buffer: Variable size: set in CONTROL[2]	CIP Request: Request size: set in CONTROL[7]
	CIP Response: Starting position: set in CONTROL[3] Response size: reported in CONTROL[8] NOTE: If the response offset is smaller than the request size, the response data overwrites part of the request.

The format of the data buffer’s CIP request and CIP response is described, below.

NOTE: Structure both the request and response in little endian order.

Request:

Byte offset	Field	Data type	Description
0	Service	Byte	Service of the explicit message
1	Request_Path_Size	Byte	The number of words in the Request_Path field
2	Request_Path	Padded EPATH	This byte array describes the path of the request—including class ID, instance ID, etc.—for this transaction
...	Request_Data	Byte array	Service specific data to be delivered in the explicit message request—if none, this field is empty

Response:

Byte offset	Field	Data type	Description
0	Reply Service	Byte	Service of the explicit message + 16#80
1	Reserved	Byte	0
2	General Status	Byte	EtherNet/IP General Status
3	Size of Additional Status	Byte	Additional Status array size—in words
4	Additional Status	Word array	Additional status1
...	Response Data	Byte array	Response data from request, or additional detected error data if General Status indicates a detected error
1. Refer to The CIP Networks Library, Volume 1, Common Industrial Protocol at section 3-5.6 Connection Manager Object Instance Detected Error Codes;