Acyclic Data Exchange Between Controller And Pn/Can Link - Siemens Simatic Operating Instructions Manual

4.1.2.3

Acyclic data exchange between controller and PN/CAN LINK

Acyclic data exchange
The PN/CAN LINK provides multiple data records for the CANopen Manager module on the
PROFINET side, which the S7 user program can access with the acyclic PROFINET IO
services RDREC (read data record) und WRREC (write data record). These data records are
not available to the configured CANopen slaves.
16 data records are available for SDO reading and for SDO writing.
The data record indices in use are 0x200 to 0x20F.
Note
A data record for a (sub)module in PROFINET is uniquely defined by an "index" that
specifies the data record number. The index is a 32-bit integer. Different data records differ
in their index.
Each data record represents an independent communication channel that can be used
independently of the other channels. SDO communication is initiated with the corresponding
data record with the help of the services RDREC (read data record) and WRREC (write data
record). A WRREC is always run first to transfer the desired SDO command to the PN/CAN
LINK; it is followed by a RDREC to the same index to retrieve the result. RDREC may have
to be repeated multiple times if the PN/CAN LINK returns information that SDO access has
not yet finished (status code = "Busy").
A maximum of 128 bytes are transmitted during an SDO access.
SIMATIC PN/CAN LINK
Operating Instructions, 03/2018, A5E39895388-AB
Functions
4.1 CANopen
31