Siemens CP 243-2 - Manual (Page 124)

Command Interface
5-56
SIMATIC NET CP 243-2 AS-i Master
C79000-G8976-C142/02
5.2.30 Read_AS-i_Slave_ID_String
Purpose
With this call, an identification 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 always supplies 223 bytes of reply data. The actual
number of ID bytes sent by the AS-i slave is signaled by the AS-i master in byte 2
of the receive buffer (number of ID 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.
Note
In contrast to other jobs, in this job, the bytes containing the bits ”Follow” and
”Valid” are also transferred (see slave profile 7.4).
Structure of the Job Data in the Send Buffer
Bank Byte Meaning
2 0 Command number 42
H
2 1 Slave address
Structure of the Job Data in the Receive Buffer
Bank Byte Meaning
2 0 Echo of the command number 42
H
2 1 Command status
2 2 Number of ID bytes
2 3 String byte (1)
2 4 String byte (2)
... ... .....
... ... String byte (n–1)
... ... String byte (n)
Maximum value for n=220