Sercos Communication State Machine and Communication Phases
The Sercos communication state machine uses the communication state NRT (Non-Real-Time) and five Communication Phases (CP) from CP0 to CP4.
Communication States/Communication Phases
|
Communication state/communication phase |
Description |
|---|---|
|
NRT (non-real-time) |
Setup of Ethernet communication oFirst state after power-on or after detected synchronization error oEthernet communication active, master can send and slaves can receive UCC telegrams (store-and-forward or cut-through) |
|
Communication phase CP0 |
Identification of participating slaves: oMDT0 with MST is sent, AT0 acknowledges presence and returns Sercos address |
|
Communication phase CP1 |
Configuration of slaves for non-cyclic communication via SVC: oMaster sends MDT0 and MDT1 as well as AT0 and AT1 containing C-DEV controls for slaves (identification, topology) oSlaves respond with appropriate status information in their allocated S-DEV controls |
|
Communication phase CP2 |
Configuration of Sercos communication parameters for CP3 and CP4: oMaster transmits length of MDTs and ATs with offsets for SVC and RTD of slaves) oCommunication via SVC oCondition for transition to CP3: procedure command S-0-0127 successful |
|
Communication phase CP3 |
Configuration of application parameters: oStructure of MDT complete (offsets for SVC and RDT), configured application data not yet evaluated oCondition for transition to CP4: procedure command S-0-0128 successful |
|
Communication phase CP4 |
Sercos communication active: oSercos communication fully established, bus ready for operation |
Transitions to higher communication phases are referred to as “phase-up”, transitions to lower communication phases as “phase-down”.
