Siemens CP 243-2 - Manual (Page 50)

Access to the Data of the AS-i Slaves
3-2
SIMATIC NET CP 243-2 AS-i Master
C79000-G8976-C142/02
3.1 Access to the Binary Data of the AS-i Slaves
3.1.1 Addressing the AS-i Slaves in the User Program
Requirements
Before you can access the I/O data of the AS-i slaves, the following requirements
must be met:
S
Deactivate the filtering of the analog inputs for the CP 243–2 in the system data
block of the S7–200 CPU.
S Set the “PLC_RUN” bit (bit 7) in the digital control byte to ’1’ at the beginning of
the cyclic program.
S
Access to the I/O data of the slaves is then only allowed when the “CP_Ready”
bit (bit 1) in the digital status byte is set to ’1’.
Access to the Binary Values
The CP 243-2 assigns four bits (a nibble) in the input and output data area for
each AS-i slave. The PLC can write (slave output data) and read (slave input data)
this nibble.
This allows bi-directional slaves to be addressed.