Editorial Technical Reference

Central PLC controller: EtherCAT bus master that coordinates distributed I/O, servos and drives

Central PLCs as EtherCAT bus masters · One controller coordinating distributed I/O, servos and drives, cycle time and jitter, segment size, interpolation and electronic cams

This page covers the central controller of a machine or line when its I/O and drives are distributed on an EtherCAT network: one PLC acts as the bus master, runs the motion and logic, and exchanges process data with every device each cycle. Ask three things first: what cycle time and synchronisation the controller holds with your device count, which drives and I/O it supports on the bus, and which motion functions (interpolation, cams) it provides.

Central PLCs and bus controllers that act as EtherCAT masters for distributed I/O, servo drives, steppers and inverters on machines and lines. Compact PLCs with local and expansion I/O are covered on the Programmable logic controller (PLC) page. Industrial PCs, safety controllers and building or lighting controllers are outside this page.

CNFX editorial research · Sources checked October 12, 2026 · 3 sources

Check bus performance Check motion and device support

Illustration of an open control cabinet with a row of modular PLC units, terminal blocks, network switches and power supplies, and an engineer holding a tablet beside automated robot cells — Illustration: control cabinet with a modular PLC and network switches beside robot cells

Start with your task

Check bus performanceCycle time, jitter and devices. Check motion and device supportInterpolation, cams, drives.

Check bus performance: cycle time, jitter and device count

The EtherCAT Technology Group states that EtherCAT, standardised in IEC 61158, was developed for short cycle times of 100 µs or less, low jitter for synchronisation of 1 µs or less and low hardware cost; up to 65,535 devices can be connected to one segment in line, tree or star topology, copper links run up to 100 m between nodes with fibre such as 100BASE-FX beyond that, and the effective data rate of a telegram exceeds 90%. Only the EtherCAT MainDevice may actively send frames; other nodes forward them, and distributed clocks synchronise the nodes in hardware with compensation for propagation delays. [1]

The ETG also states that the master can refresh drives at a short cycle time while sampling I/O at a longer one, that EtherCAT can assign addresses automatically, and that the architecture reduces CPU load by 25–30% compared with other bus systems at the same cycle time. [1] [2]

Editorial calculation: at a 100 µs cycle the master exchanges process data 10,000 times per second; at 1 ms, 1,000 times. Ask the supplier for the cycle time it guarantees with your actual number of axes and I/O modules, not the protocol's lower limit. [1]

Give the supplier the number of servo axes, steppers, inverters and I/O points, required cycle time and synchronisation, cam or interpolation needs, programming standard (for example CODESYS), and the HMI and higher-level networks to connect.

Check motion functions and supported devices

Xinje describes its XDH series EtherCAT bus controller as integrating EtherCAT, communicating with its own distributed I/O, DS5C2 servo drives, DP3C steppers and VH6 inverters as well as other standard EtherCAT devices, and offering larger program capacity and faster processing. It lists three-axis linear, circular-arc and spiral interpolation and an electronic cam function in which up to 32 cam tables can be loaded, each storing up to 1,000 key points, used on capping, pillow packaging and blow moulding machines, plus look-ahead to protect accuracy where parts of the system lag. [3]

Xinje's download list for the series includes a CODESYS native platform device package, an XD/XL/XG series software manual and a flying shear process library. [3] Editorial calculation: 32 cam tables × 1,000 key points is up to 32,000 stored cam points. [3]

Editorial note: confirm which non-Xinje EtherCAT devices have been tested with the controller, and whether cam and interpolation run in the same cycle as the bus or in a slower task.

Central EtherCAT master, mixed cycle times and bus controllers with motion libraries

The choice is where I/O sits and how it is synchronised.

Architecture	What the source states	Ask for
Central EtherCAT master with distributed devices	≤100 µs cycles; ≤1 µs jitter; up to 65,535 devices per segment. [1]	Guaranteed cycle with your device count.
Mixed cycle times	Drives refreshed fast, I/O sampled slower. [1]	Task configuration.
Bus controller with motion library (XDH)	3-axis interpolation; 32 cam tables × 1,000 points. [3]	Motion function list.

MainDevice, distributed I/O, drives and distributed clocks on an EtherCAT network

Module	Role	Fix in the order
Central controller (MainDevice)	Sends EtherCAT frames and runs logic and motion. [1] [3]	Model; program capacity.
Distributed I/O	Slice modules can each be a node. [1]	Modules and counts.
Servo drives and steppers	Synchronised motion, e.g. DS5C2, DP3C. [3]	Drive models.
Inverters	Speed control, e.g. VH6. [3]	Inverter models.
Distributed clocks	Hardware synchronisation of nodes. [1]	Sync requirement.
Software	CODESYS device package; process libraries. [3]	Programming environment.

Supply, program memory, I/O count and scan time of the master PLC

Field	What it means and published values	Ask the supplier for
Rated Supply Voltage (V DC)	Controller supply.	Voltage.
Power Consumption (W)	Controller load.	Power.
Program Memory (KB)	Xinje cites larger program capacity on the XDH. [3]	Capacity in KB or steps.
Digital I/O Points (points)	Distributed over the bus; up to 65,535 devices per segment. [1]	Points per module and total.
Analog I/O Channels (channels)	Distributed analogue modules.	Channels and resolution.
Scan Time (ms)	EtherCAT designed for ≤100 µs cycles. [1]	Guaranteed cycle with your load.
Operating Temperature (°C)	Cabinet ambient.	Range.
Storage Temperature (°C)	Storage range.	Range.
Relative Humidity (%)	Cabinet conditions.	Range.
Ingress Protection	Cabinet-mounted controller.	Rating.
Vibration Resistance (g)	Mechanical test level.	Test standard and level.
Shock Resistance (g)	Mechanical test level.	Test standard and level.
Weight (kg)	Controller weight.	Weight.
Dimensions (W x H x D) (mm)	Rail space in the cabinet.	Dimensions.

Send the device list, timing and motion needs together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Devices: [servo axes; steppers; inverters; I/O points]
Timing: [cycle time; synchronisation]
Motion: [interpolation; cams; flying shear]
Software: [programming environment]
Networks: [HMI; MES; remote access]
Environment: [cabinet temperature]

See manufacturer records Send an enquiry through CNFX

Buyer questions

How fast is an EtherCAT bus?

The EtherCAT Technology Group states it was designed for cycle times of 100 µs or less with synchronisation jitter of 1 µs or less. [1]

How many devices can one EtherCAT controller address?

Up to 65,535 devices can be connected to one EtherCAT segment, according to the EtherCAT Technology Group. [1]

What motion functions does an EtherCAT bus controller offer?

Xinje lists three-axis linear, circular and spiral interpolation and electronic cams with up to 32 tables of 1,000 key points for its XDH series. [3]

Sources and what still needs a direct check

Sources checked 2026-10-12. The EtherCAT Technology Group describes its own technology; Xinje describes its own controller.

EtherCAT Technology Group — EtherCAT technology introduction ↗ Industry organisation technical page Return to text ↑
EtherCAT Technology Group — Why use EtherCAT ↗ Industry organisation page Return to text ↑
Xinje — XDH series EtherCAT bus controller ↗ Maker product page Return to text ↑

Still to check yourself

Confirm guaranteed cycle time with your device count.
Check supported drives and I/O on the bus.
Confirm motion functions and their task timing.
Confirm programming environment and libraries.
Verify the legal supplier and factory.