103BCommunication
10.4 AS-i
S7-1200 Programmable controller
System Manual, 11/2011, A5E02486680-05
457
The following simple program illustrates how the assignment works:
Input 2.0 is polled in this program. In the AS-i system, this input belongs to slave1 (Input byte
2, bit 0). Output 4.3, which is then set, corresponds to AS-i slave 3 (Output byte 4, bit 3)
Transferring AS-i analog values
You can access analog data of an AS-i slave through the process image of the PLC if you
have configured this AS-i slave in STEP 7 as an analog slave.
If you did not configure the analog slave in STEP 7, you can only access the data of the AS-i
slave through the acyclic functions (data record interface). In the user program of the CPU,
AS-i calls are read and written using the RDREC (read data record) and WRREC (write data
record) distributed I/O instructions.
Note
A configuration of the AS-i slaves specified through STEP 7 and downloaded into the S7
station is transferred by the CPU on the AS-i master CM 1243-2 during S7 station start-up.
Any existing configuration that was determined through the "System assignment" online
function (Page 457) ("ACTUAL -> EXPECTED") will be overwritten.
Further information
You will find detailed information on the AS-i CM 1243-2 in the "CM 1243-2 and AS-i data
decoupling unit DCM 1271 for SIMATIC S7-1200" Manual.
10.4.2.2
Configuring slaves without STEP 7
If the parameter "System assignment" is selected, the system will automatically assign AS-i
slave addresses to logical I/O addresses.
This causes the AS-i master to reserve a 62-byte data area in the I/O area of the SIMATIC.
Access to the digital data is performed here in bytes (in other words, one byte is assigned to
each AS-i digital slave).
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 inspection window of the AS-i master CM 1243-2.
