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The assignment of the AS-i connections of the AS-i digital slaves to the data bits of the
assigned byte is indicated in the inspector window of the AS-i master CM 1243-2:
You can access the data of the AS-i slaves in the user program by means of the displayed
I/O addresses with the appropriate bit logic operations (e.g. "AND") or bit assignments.
Access with configuration of the AS-i slaves with STEP 7
When you configure the AS-i slaves in STEP 7, the I/O address for accessing the data from
the user program is displayed in the inspector window for the respective AS-i slave.
You can access the data of the AS-i slaves in the user program by means of the displayed
I/O addresses with the appropriate bit logic operations (e.g. "AND") or bit assignments.
6.1.2
Special characteristics of Combined Transaction Type Slaves
If you are using the AS-i slaves in accordance with CTT1 ... 5, the "I/O bits" may be used for
special transfer functions. For further details, please refer to the documentation of the
respective AS-i slave.
The following applies to these protocol bits:
● In the input direction, the AS-i master CM 1243-2 sets the value "0".
● In the output direction, the AS-i master CM 1243-2 ignores the bits.
For a description of how to access the AS-i analog slaves, see section "Transferring AS-i
analog values (Page 51)".
AS-i master CM 1243-2 and AS-i data decoupling unit DCM 1271 for SIMATIC S7-1200
Manual, 04/2013, A5E02655230010A/RS-AA/003
Data exchange between the user program and AS-i slaves
6.1 Transferring AS-i digital values
49
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