Siemens SIMATIC ET 200AL, System Manual

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Communication
Function Manual, 05/2021, A5E03735815-AJ
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Instructions for Freeport communication
There are 3 instructions available for the dynamic configuration in the user program for
Freeport communication. The following applies to all 3 instructions: the previously valid
configuration data is overwritten but not stored permanently in the target system.
•
The "Port_Config" instruction is used for the program-controlled configuration of the
relevant port of the communications module.
• The "Send_Config" instruction is used for the dynamic configuration, for example of time
intervals and breaks in transmission (serial transmission parameters) for the relevant port.
• The "Receive_Config" instruction is used for dynamic configuration, for example of
conditions for the start and end of a message to be transferred (serial receive parameters)
for the relevant port.
Instructions for 3964 (R) communication
There are 2 instructions available for dynamic configuration in the user program for 3964 (R)
communication. The following applies to the instructions: the previously valid configuration
data is overwritten but not stored permanently in the target system.
•
The "Port_Config" instruction is used for the program-controlled configuration of the
relevant port of the communications module.
• The "P3964_Config" instruction is used for the dynamic configuration of protocol
parameters.
Properties of the USS protocol
• Simple, serial data transfer protocol with cyclic message frame traffic in half duplex mode
that is tailored to the requirements of drive technology.
• Data transfer works according to the master-slave principle.
– The master has access to the functions of the drive and can, among other things,
control the drive, read status values and read and write the drive parameters.
Data exchange using USS communication
The communications module is the master. The master continuously sends frames (job
frames) to the up to 16 drives and expects a response frame from each addressed drive.
A drive sends a response frame under the following conditions:
•
When a frame is received without errors
• When the drive is addressed in this frame
A drive must not send if these conditions are not met or the drive was addressed in the
broadcast.
The connection to the relevant drives exists for the master once it receives a response frame
from the drive after a specified processing time (response delay time).