Siemens S7-1200 System Manual page 584

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Communication

The digital input module (AS-i SM-U, 4DI) in the AS-i network above has been assigned I/O

address 2. By clicking on the digital input module, the "I/O addresses" tab in the device

"Properties" displays the I/O address, as shown below:

You can access the data of the AS-i slaves in the user program by using their I/O addresses

with the appropriate bit logic operations (for example, "AND") or bit assignments. 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 CPU 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.

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 CM1243-2 during S7 station start-up.

Any existing configuration that was determined through the "System assignment" online

function (Page 582) ("ACTUAL -> EXPECTED") will be overwritten.

Further information

You can find detailed information on the AS-i master CM 1243-2 in the "AS-i master CM

1243-2 and AS-i data decoupling unit DCM 1271 for SIMATIC S7-1200" Manual

(http://support.automation.siemens.com/WW/view/en/50414115/133300).

S7-1200 Programmable controller

System Manual, 03/2014, A5E02486680-AG