Siemens SIMATIC ET 200SP Manual page 99

Command processing in the user program
Structure the command processing in the user program as follows:
1. Specify the command call (Page 103) in a send buffer in the user program.
2. Send this data record call to the CM AS-i Master ST with Write_data_record (data
record 2).
3. Then, query the status of the command processing in the input range for digital values
(cyclic services). The status information is stored in the first byte reserved for it (byte 0) in
bits 4 to 7 of the input range (status nibble).
4. Different reactions occur depending on the result of the status evaluation. You can find
these in the following sequence chart. Details on the meaning of the status nibble can be
found in the "Coding of the status nibble" table.
To complete the command processing, you must always issue a Read_data_record (data
record 2) job either to obtain further information or to apply the response data.
Figure 9-2
AS-Interface master CM AS-i Master ST (3RK7137-6SA00-0BC1)
Manual, 07/2017, A5E02655262020A/RS-AD/004
9.3 Command interface with controllers of other manufacturers
Flowchart
Using the command interface
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