Functions
5.2 CAN transparent
SIMATIC PN/CAN LINK
Operating Instructions, 03/2022, A5E39895388-AC
71
5.2.6
Cyclic data exchange between controller and PN/CAN LINK for programmed
CAN messages
"Transmit proxies" and "Receive proxies" can be set up in the TIA Portal.
These proxies serve as a "communication channel" that enables the S7 user program to send
and receive any CAN messages not configured beforehand.
The use of multiple transmit / receive proxies facilitates programming of the S7 user program
because independent communication channels are involved.
Example of transmit proxy module:
Two code locations want to transmit CAN messages. When you set up two transmit proxies,
these messages do not have to be synchronized or matched. Each code location uses its own
proxy.
Example of receive proxy module:
Because each receive proxy module has its own "receive filter list", you can use multiple proxy
modules to pre-filter messages by CAN ID, for example, one receive proxy for "commands"
only and one receive proxy for "status messages".
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.
Содержание SIMATIC PN/CAN LINK
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