Siemens SIMATIC S7-1200 System Manual page 1255

Hide thumbs Also See for SIMATIC S7-1200:

Table of Contents

Table 13- 132 MB_CLIENT instance data block user accessible static variables

Blocked_Proc_Timeout

Table 13- 133 MB_CLIENT protocol errors

Response code to

Modbus client

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Data type Default

Amount of time (in seconds) to wait upon a blocked Modbus client

instance before removing this instance as being ACTIVE. This can

occur, for example, when a client request has been issued and then

application stops executing the client function before it has completely

finished the request. The maximum S7-1200 limit is 55 seconds.

Modbus unit identifier:

A Modbus TCP server is addressed using its IP address. As a result,

the MB_UNIT_ID parameter is not used for Modbus TCP addressing.

The MB_UNIT_ID parameter corresponds to the slave address in the

Modbus RTU protocol. If a Modbus TCP server is used for a gateway to

a Modbus RTU protocol, the MB_UNIT_ID can be used to identify the

slave device connected on the serial network. The MB_UNIT_ID would

be used to forward the request to the correct Modbus RTU slave ad-

Some Modbus TCP devices may require the MB_UNIT_ID parameter to

be initialized within a restricted range of values.

Time in seconds that the MB_CLIENT waits for a server to respond to a

Indicates whether the connection to the assigned server is connected

or disconnected: 1=connected, 0=disconnected

Modbus protocol errors

Function code not supported

Data length error

Data address error or access outside the bounds of the MB_HOLD_REG address area

Data value error

Data diagnostic code value not supported (function code 08)

Communication processor and Modbus TCP

13.8 Legacy Modbus TCP communication