EtherCAT Information
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10/07/2013
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4.8 PDO mapping
PDO mapping refers to the mapping of application objects (real-time data, e.g. object
6004h "Position value" from the object dictionary into Process Data Objects, e.g.
Object 1A00h (1
st
Transmit PDO).
The current mapping can be read via corresponding entries in the object dictionary,
the so-called mapping tables. The number of mapped objects that are listed
subsequently is found at the top of the mapping table (subindex 0). The tables are
located in the object dictionary in index 0x1600 ff. for the RxPDOs and 0x1A00ff for
the TxPDOs.
4.9 EtherCAT State Machine (ESM)
The Application Management contains the EtherCAT State Machine, which describes
the states and state changes of the slave application. Apart from a few details, the
ESM corresponds to the CANopen Network Management (NMT). In order to enable
reliable starting behavior the "Safe Operational" state has been introduced in
EtherCAT. In this state valid entries are transmitted, while the outputs remain in safe
status.
Figure 8: EtherCAT State Machine
Status
Description
IP
Start Mailbox Communication
PI
Stop Mailbox Communication
PS
Start Input Update
SP
Stop Input Update
SO
Start Output Update
OS
Stop Output Update
OP
Stop Output Update, Stop Input Update
SI
Stop Input Update, Stop Mailbox Communication
OI
Stop Output Update, Stop Input Update, Stop Mailbox Communication