Siemens SIMATIC NET CP 243-2, Manual

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Command Interface
5-55
SIMATIC NET CP 243-2 AS-i Master
C79000-G8976-C142/02
5.2.29 Read_AS-i_Slave_Parameter_String
Purpose
With this call, a parameter 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 223 bytes of reply data. The actual number of
parameter bytes sent by the AS-i slave is signaled by the AS-i master in byte 2 of
the receive buffer (number of parameter 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 41
H
2 1 Slave address
Structure of the Job Data in the Receive Buffer
Bank Byte Meaning
2 0 Echo of the command number 41
H
2 1 Command status
2 2 Number of parameter bytes
2 3 String byte (1)
2 4 String byte (2)
... ... .....
... ... String byte (n–1)
... ... String byte (n)
Maximum value for n=220