Siemens DP/AS-Interface Link 20E, Manual

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Using the Command Interface
123
DP/AS-Interface Link 20E
Release 11/2002
C79000-G8976-C138–04
3.3.31 Read_AS-i_Slave_Diagnostic_String
Purpose
With this call, a diagnostic string complying with AS-i slave profile 7.4 can be read
from the AS-i slave with the AS-i slave address specified in the send buffer. The
AS-i master supplies up to 221 bytes of response data. The number of diagnostic
bytes actually sent by the AS-i slave is signaled by the AS–i master in byte 0 of the
receive buffer (number of diagnostic bytes).
If the AS-i slave sends a string longer than 220 bytes, the AS-i master aborts the
string transfer and terminates the job with an error. The received data are then not
made available to the user program.
As long as the string transfer is active, there is no user/analog data exchange with
the addressed AS-i slave.
Structure of the Job Data in the Send Buffer
Byte Meaning
0 Command number 43
H
1 Slave address
Structure of the Response Data in the Receive Buffer
Byte Meaning
0 Number of diagnostic bytes
1 String byte (1)
2 String byte (2)
... .....
... String byte (n-1)
... String byte (n)
Maximum value for n=220