Siemens S7-1200 System Manual page 317

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Table of Contents

Parameter and type

The RDREC and WRREC instructions operate asynchronously, that is, processing covers

multiple instruction calls. Start the job by calling RDREC or WRREC with REQ = 1.

The job status is displayed via output parameter BUSY and the two central bytes of output

parameter STATUS. The transfer of the data record is complete when the output parameter

BUSY has been set to FALSE

A value of TRUE (only for one scan) on the output parameter VALID (RDREC) or DONE

(WRREC) verifies that the data record has been successfully transferred into the target area

RECORD (RDREC) or to the target device (WRREC). In the case of the RDREC, the output

parameter LEN contains the length of the fetched data in bytes.

The output parameter ERROR (only for one scan when ERROR = TRUE) indicates that a

data record transmission error has occurred. In this case, the output parameter STATUS

(only for the one scan when ERROR = TRUE) contains the error information.

Data records are defined by the hardware device manufacturer. Refer to the hardware

manufacturer's device documentation for details about a data record.

If a DPV1 slave is configured via GSD file (GSD rev. 3 and higher) and the DP interface of

the DP master is set to "S7 compatible", then you may not read any data records from the

I/O modules in the user program with "RDREC" or write to the I/O modules with "WRREC".

In this case, the DP master addresses the wrong slot (configured slot + 3).

Remedy: set the interface of the DP master to "DPV1".

The interfaces of the "RDREC" and "WRREC" instructions are identical to the "RDREC" and

"WRREC" FBs defined in "PROFIBUS Guideline PROFIBUS Communication and Proxy

Function Blocks according to IEC 61131-3".

If you use "RDREC" or "WRREC" to read or write a data record for PROFINET IO, then

negative values in the INDEX, MLEN, and LEN parameters will be interpreted as an

unsigned 16-bit integer.

S7-1200 Programmable controller

System Manual, 03/2014, A5E02486680-AG

8.3 Distributed I/O (PROFINET, PROFIBUS, or AS-i)

Length of the fetched data record information (RDREC)

Maximum byte length of the data record to be transferred

Target area for the fetched data record (RDREC)

Data record (WRREC)

Extended instructions