No. 42: Read_String - Siemens SIMATIC ET 200SP Manual

Using the command interface
9.4 Description of the AS-i commands
9.4.31

No. 42: Read_String

Meaning
This command causes the AS-i slave to read an identification string in accordance with AS-
i slave profile 7.4 with the AS-i slave address specified in the send buffer. The AS-i master
supplies up to 221 bytes of reply data. The AS-i master signals the actual number of ID bytes
sent by the AS-i slave in Byte 0 of the receive buffer.
If the AS-i slave sends an ID string longer than 220 bytes, the AS-i master aborts string
transfer and terminates the job with an error. The received data is not made available to the
user program.
As long as the transmission of the identification string is running, there is no transfer of
user/analog data with the addressed AS-i slave.
Note
In a deviation from normal procedure, this command also transfers the bytes that contain the
bits "Follows" and "Valid".
For further details, refer to AS-i slave profile 7.4
Structure of the job data in the send buffer
Table 9- 59 Structure of the job data in the send buffer
Byte
0
1
Structure of the reply data in the receive buffer
Table 9- 60 Structure of the reply data in the receive buffer
Byte
0
1
2
...
n - 1
n
Maximum value for n = 220
150
Meaning
Command number: 42
H
Slave address
Meaning
Number of ID bytes
ID string byte 1
ID string byte 2
...
ID string byte n - 1
ID string byte n
AS-Interface master CM AS-i Master ST (3RK7137-6SA00-0BC1)
Manual, 07/2017, A5E02655262020A/RS-AD/004