Siemens Simatic Operating Instructions Manual page 51

Transmit proxy module
CAN messages can be transmitted from the S7 user program with the help of a transmit
proxy module. It comprises cyclic PROFINET input and output data.
In the output data from the S7 controller to the PN/CAN LINK, the following information is
transmitted for the frame to be sent to the PN/CAN LINK:
● Message ID
● Length
● User data
● Flag, indicating whether RTR or CAN data message
In the input data from the PN/CAN LINK to the S7 controller, the PN/CAN LINK
acknowledges entry of the message in the CAN transmit buffer in the PN/CAN LINK. This
does not always mean, however, that the message has been transmitted on the CAN bus.
Note
The order of the data bytes in the CAN messages to be sent is not changed in the PN/CAN
LINK. Any necessary adaptation to compensate for "endianness" must be made in the
S7 user program.
Note
For values made up of multiple bits, the first bit is the MSB and the last bit is the LSB.
Example: Byte.Bit 3.0 ... 4.6 = 2 means: Byte 3 bit 0 = "0", byte 4 bit 7 = "1" and
byte 4 bit 6 = "0".
SIMATIC PN/CAN LINK
Operating Instructions, 03/2018, A5E39895388-AB
Functions
4.2 CAN transparent
49