Manual

Doc.Id. HMSI-216-117
CM CANopen Module for SIMATIC S7-1200
Doc.Rev. 1.00
Chapter 3
3. Transparent CAN Mode
The CM CANopen Module for SIMATIC S7-1200 integrates Transparent CAN 2.0A (11 bit identifiers).
With this protocol, the module allows transmission of any CAN frame from the PLC regardless of the
overlaying CAN protocol, and is capable of receiving a number of predefined CAN frames from the
CAN network. No other functionality is available.
CAN 2.0A is the underlying protocol of CANopen, directly working on the bus. During configuration
in TIA Portal, Transparent CAN can be selected in the Options menu. When this configuration is down
-
loaded to the module, the CANopen functionality is not possible to use. If CANopen functionality is to
be reactivated, a new configuration from TIA Portal will have to be downloaded. It is not possible to
change between CAN and CANopen at runtime.
Each CAN frame is tagged with an identifier. Only received frames with an identifier specified by the
function block CAN_CTRL will be forwarded to the PLC. The data in the frame is then available for
the user to interpret. When sending a frame, the user specifies the data and adds a valid identifier before
sending it to the module.
To facilitate the use of Transparent CAN, separate PLC function blocks are available
1
. They are de-
scribed in “Transparent CAN Function Blocks” on page 47. The blocks give the designer of the PLC
program the possibility to integrate Transparent CAN functionality (sending, receiving, configuration)
into the PLC program, thereby making it possible to implement customer specific CAN protocols.
Note: The receive buffer can hold up to 256 unread received messages
1. The function blocks can be downloaded from www.hms-networks.com/can-for-S7-1200.