The MotionLinx-Ai module’s’ CoE definition contains the capacity for 6 Receive PDOs (RxPDO) and 6 Transmit PDOs (TxPDO). By default 3 of the RxPDOs are pre-defined and enabled leaving 3 spare and by default 2 of the TxPDOs are pre-defined and enabled leaving 4 spare.
The TwinCAT IDE provides the tools to allow you to edit and/or disable any of the pre-defined RxPDOs or TxPDOs as well as assign previously defined and select SDO Dictionary Items into your RxPDOs and/or TxPDOs. This allows you to get automatic and cyclical updates to data through the PDO mechanism for the SDO items without having to explicitly initiate a separate SDO read/write for this same data.
Customizing PDO Guidelines and Limitations
When you configure one of the spare PDOs and/or modify one of the pre-defined PDOs, there are some basic guidelines you need to follow:
• Maximum of 10 objects per PDO
• Maximum of 200 bytes total for all enabled TxPDOs
• Maximum of 200 bytes total for all enabled RxPDOs
• Total length of mapped objects must align on 4-byte boundaries