Siemens SIMATIC NET CP 243-2, Manual

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Command Interface
5-57
SIMATIC NET CP 243-2 AS-i Master
C79000-G8976-C142/02
5.2.31 Read_AS-i_Slave_Diagnostic_String
Purpose
With this call, an diagnostic string complying with the 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 223 bytes of reply data. The number of diagnostic
bytes actually sent by the AS-i slave is signaled by the AS-i master in byte 2 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
Bank Byte Meaning
2 0 Command number 43
H
2 1 Slave address
Structure of the Job Data in the Receive Buffer
Bank Byte Meaning
2 0 Echo of the command number 43
H
2 1 Command status
2 2 Number of diagnostic bytes
2 3 String byte (1)
2 4 String byte (2)
... ... .....
... ... String byte (n–1)
... ... String byte (n)
Maximum value for n=220