System bus (CAN) with Ser vo PLC & Drive PLC
General information
2-8
l
PLC-Systembus EN 1.1
2.5.2 Sync telegram for cyclic process data
A special telegram, the Sync telegram, is required for synchronisation when cyclic process data are
transmitted.
The Sync telegram must be generated by another bus participant. It initiates the transmission of
cyclic process data from the PLC and at the same time triggers data acceptance of cyclic process
data received in the PLC:
Sync telegram Sync telegram
CAN1_OUT CAN1_IN
1. 2. 3. 4.
Fig. 2-4 A Sync telegram is used for the synchronisation of cyclic process data (asynchronous data is not considered)
1. On receipt of a Sync telegram, the PLC transmits the cyclic process output data
(CAN1_OUT), if “Response to Sync” has been activated.
2. Once the transmission has been finished, the PLC receives the cyclic process input data
CAN1_IN).
3. With the next Sync telegram data is accepted in the PLC.
4. All other telegrams (e.g. for parameter or event-controlled process data) are asynchronously
accepted by the PLC once they have been transmitted.
Tip!
The response to a Sync telegram is configured
• via C0366 for CAN1_OUT. (^ 3-5)
• via C2375 for XCAN1_OUT ... XCAN3_OUT. (^ 4-5)
• via C2466 for FIF-CAN1_OUT. (^ 5-6)
The telegrams from CAN2_OUT and CAN3_OUT can also be transmitted after a Sync telegram.
Parameters for this functionality are set via the CAN_Management SB.
(^ 6-18)
2.5.3 Process data telegram
Structure of the process data telegram:
11 Bit 8-byte user data
Identifier Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7 Byte 8
Identifier
Information about the identifier can be found in chapter 2.3.1.
(^ 2-2)
User data
The 8-byte user data received or transmitted can be read or written by several variables of different
data types at the same time.
Detailed information about the user data can be found in the system block description in chapter
6, “System blocks”.
(^ 6-1ff)
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