EtherCAT State Machine  

The EtherCAT State Machine (ESM) is required on all EtherCAT devices. The ESM in general

• defines 5 communication states of the slave device
  • Init, Pre-Operational, Safe-Operational, Operational
  • Bootstrap is an optional state for firmware upload
• specifies initialization and error handling of the slave device
• identifies the current communication relationship between the master and slave device
  • requested and current state are accessed through the AL Control and AL Status registers

The ESM states can be transitioned as shown

Init State

• No communication to the application layer is allowed
• master only has communication to the data link registers (slave device eeprom, addressing, etc)

Pre-Operational State

• Mailbox (SDO) communication to the application layer is available
• No Process Data (PDO) communication.
• PDO register mapping should be completed. Transition to Safe-Operation will configure mapping.

Safe-Operational State

• Mailbox (SDO) communication to the application layer is available
• Slave output (tx) Process Data (PDO) communication is evaluated

Operational State

• All communication is commenced and valid

PDO Mappings 

The Cool Muscle EtherCAT slave uses dynamic switching between modes and as such there is a single fixed PDO configuration.

RxPDO

The RxPDO is the PDO received by the motor/slave device

TxPDO

The TxPDO is the PDO transmitted by the motor/slave device