Functions
5.2 CAN transparent
SIMATIC PN/CAN LINK
Operating Instructions, 03/2022, A5E39895388-AC
73
Table 5- 11 Structure of input data for transmit proxy modules (from PN/CAN LINK to S7 controller, 1
byte)
Byte.Bit Meaning
0.7 ... 0.3 Reserved, must not be evaluated
0.2
Transmit buffer overflow
Is set to "1" by the PN/CAN LINK when a CAN message could not be entered in the transmit
buffer because it is full. A corresponding diagnostic information is also sent in this case.
The bit is reset to "0" when the transmit acknowledgment bit is set to "0".
0.1
Last data faulty
Is set to "1" by the PN/CAN LINK when the "Number of data bytes" is greater than 8.
The bit is reset to "0" when the transmit acknowledgment bit is set to "0".
0.0
Transmit acknowledgment
Is set to "1" by the PN/CAN LINK as soon as the send bit is "1". When the send bit changes
to "0", the PN/CAN LINK sets the send acknowledgment bit to "0" as soon as it has
transmitted the message to be sent to the send buffer of the CAN controller.
Receive proxy module
CAN messages can be received from the S7 user program with the help of a receive proxy
module. The module manages a list of message IDs (filters) on the PN/CAN LINK side that it
receives on the CAN bus.
The list can be filled during configuration and changed during runtime from the S7 user
program by writing a corresponding data record.
If a corresponding CAN message is received, it is entered in a receive buffer. The message is
transmitted from this buffer to the S7 controller in the cyclic input data. The size of the
receive buffer is specified in the configuration.
With the help of the output data (from the S7 controller to the PN/CAN LINK) the S7 user
program can:
•
Acknowledge the successful transmission of a CAN message from the PN/CAN LINK to the
S7 controller
•
Instruct the PN/CAN LINK to ignore the receive filter As a result, all CAN messages are
copied to the receive buffer.
•
Instruct the PN/CAN LINK to delete all CAN messages in the receive buffer
In the input data from the PN/CAN LINK to the S7 controller, the PN/CAN LINK transmits
received CAN messages and information on whether there was a receive buffer overflow.
Such an overflow occurs when too many CAN messages with matching message ID were
received before they could be transmitted to the S7 controller.
Note
The order of the data bytes in the received CAN messages is not changed in the PN/CAN LINK.
Any necessary adaptation to compensate for "endianness" must be made in the S7 user
program.
Summary of Contents for SIMATIC PN/CAN LINK
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