One language for drives — from different vendors
EtherCAT is an open real-time bus. CiA 402 is the servo drive profile: where a parameter lives, how to enable the drive and reset an error.
Bus and drive profile
EtherCAT is an open real-time industrial bus over ordinary Ethernet. A frame passes through all devices in turn, and each one takes its data and puts its answer on the fly. That is why one master serves the axes and I/O of an area in one cycle.
CiA 402 is a drive profile: a single language for controlling a servo drive. It defines where to find a parameter, how to enable the drive, how to reset a fault and what the state machine is. CANopen over EtherCAT carries this profile into the EtherCAT network.
Together they make drives from different manufacturers interchangeable in the axis model: basic data sit at the same addresses.
The bus and profile are open: their specifications are available to manufacturers, and devices from different makers work on one bus without gateways. In SyncTwin this underlies the whole equipment level — from axis tuning to the shadow of the running line, where drive and sensor feedback from the same bus is compared with the model’s response.
- EtherCATAxes and I/O from different vendors — on one real-time bus.
- Slave stateThe master brings every device up to the OP operational state.
- CANopen over EtherCATCarries the CiA 402 profile into the EtherCAT network.
The drive’s path to motion
| Command | Value | Result |
|---|---|---|
| Shutdown | 0x06 | Switch-on disabled → ready to switch on |
| Switch On | 0x07 | → switched on: power applied |
| Enable Operation | 0x0F | → operation enabled: torque held |
| Disable Voltage | 0x00 | → switch-on disabled: coasting |
| Quick Stop | 0x02 | → quick stop |
| Fault Reset | 0x80, edge | Fault clearing |
| Mode | Code | Purpose |
|---|---|---|
| CSP | 8 | Cyclic synchronous position — the working mode for CNC |
| CSV | 9 | Cyclic synchronous velocity |
| CST | 10 | Cyclic synchronous torque |
| PP, PV | 1, 3 | Profile position and velocity |
| HM | 6 | Homing |
Status word
The bits say: ready, switched on, operation enabled, fault, quick stop, switch-on disabled, warning, target reached.
Key objects
Control word and status word, mode, target position, velocity and torque, actual position, velocity and torque, following error, error code.
Reference values
A specific manufacturer’s objects and units are checked against the drive catalogue during commissioning.
How a device comes into operation
| State | What is possible |
|---|---|
| INIT | Device found, no data exchange |
| PRE-OP | Reading and writing parameters over the mailbox channel |
| SAFE-OP | The device sends inputs, outputs are not applied yet |
| OP | Operational state: cyclic exchange both ways |
Distributed clocks
One master and the devices’ common clock keep drives in one cycle phase — the basis of synchronous motion of a machine’s axes.
Synchronisation by location
Units of one box machine are in one cycle. Between boxes — handshakes; hard synchronisation there is solved by common time at hardware level.
Parameters — over the bus
The drive object dictionary is read over the bus; parameters are written to the drive’s RAM, to permanent memory — with a separate button.
The drive — by the profile, the fact — from the bus
- Mode — by the axis roleA machine axis is position, a conveyor is velocity; the role selects the drive mode.
- The fact — from the drive status wordA button's reply only proves that the request was accepted.
- Bus oscilloscopeCommand against actuals — in the browser, for axis commissioning.
- Reaction to a bus break is measuredTorque removal or a fault with reset over the bus — depending on the drive type.
- Verified on the test benchServo drives from different vendors and an I/O coupler — on one bus.
Device → profile → axis
A bus device is not an axis. A machine axis gets it only through a profile; the profile stores servo parameters, sign, backlash, zero and speed ceiling.
Each machine has its own port
Every box virtual machine has its own EtherCAT port; the port is not shared. Only one party holds the bus at any moment.
Bus snapshot
A scan takes a copy of the bus; profiles and bindings work on both the live bus and its copy.
What is confirmed on the test bench
| Structure | What is confirmed |
|---|---|
| Servo drives, manufacturer A | Operational state OP, CiA 402, CSP mode; three drives on one bus; position scale measured; on cable break — torque-off without a fault |
| Servo drive, manufacturer B | OP, CiA 402 state path, CSV mode, absolute encoder; on loss under torque — a fault reset over the bus |
| I/O coupler, manufacturer C | OP, digital output and input modules, bit order taken from the bus |
The test bench is mixed: axes, a spindle and a coupler from different manufacturers on one bus. It is a development test bench, not factory operation. Models and commissioning datasheets are in the “Supported equipment” document, on request. Compatibility of your drives is checked at the start of the implementation.
Questions about the bus and drives
Will our drives fit?
Drives on an EtherCAT bus with the CiA 402 profile fit. Compatibility of specific models is checked at the start of the implementation and fixed in the specification.
Is the manufacturer’s utility needed?
Device discovery, parameters, charts and diagnostics — in the browser. If a drive needs factory setup, this is fixed in the specification.
What if the drive is replaced with another?
On binding, the drive’s identity is recorded — model and manufacturer and product identifiers. Another drive at the same bus position is another machine: the axis does not move until it is bound again, and the screen says why.
What happens on a cable break?
It depends on the drive: on the test bench both torque-off without a fault and a fault reset over the bus were measured. Your drive’s reaction is recorded in the test protocol.
Discuss an implementation
Name the drives and I/O of your equipment — we will check profile compatibility and propose an R&D stage.
Request accessDiscuss an implementation
Describe the unit or line — we will tell you what we will verify and in what time. Target indicators are fixed in the implementation specification.
Request access