Configuring the DATA_EXCH Management Parameter

Introduction

The structure and content of the management parameter of the DATA_EXCH block is common to Modbus TCP explicit messaging.

Configuring the Management Parameter

The management parameter consists of four contiguous words:

Data source	Register	Description
Data source	Register	High Byte (MSB)	Low Byte (LSB)
Data managed by the system	Management_Param[0]	Exchange number	Two read-only bits: Bit 0 = Activity bit Bit 1 = Cancel bit
Data managed by the system	Management_Param[1]	Operation report	Communication report
Data managed by the user	Management_Param[2]	Block timeout. Values include: 0 = infinite wait other values = timeout x 100 ms, for example: 1 = 100 ms 2 = 200 ms
Data managed by the user	Management_Param[3]	Length of data sent or received: Input (before sending the request): length of data in the Data_to_Send parameter, in bytes Output (after response): length of data in the Received_Data parameter, in bytes

Activity Bit

The activity bit is the first bit of the first element in the table. The value of this bit indicates the execution status of the communication function:

1: The bit is set to 1 when the function launches.
0: The bit returns to 0 upon the completion of the execution. (The transition from 1 to 0 increments the exchange number. If an error is detected during the execution, search for the corresponding code in the operation and communication report.)

For example, you can make this declaration in the management table:

Management_Param[0] ARRAY [0..3] OF INT

For that declaration, the activity bit corresponds to this notation:

Management_Param[0].0

NOTE: The notation previously used requires configuration of the project properties in such a way as to authorize the extraction of bits on integer types. If this is not the case, Management_Param[0].0 cannot be accessed in this manner.