general best practice

Scope

Use this page for host-level and startup-level recommendations that apply across many ecmc systems.

EtherCAT rate (EC_RATE)

The default EtherCAT frame rate in ecmc is 1 kHz. For many systems this is higher than necessary and can therefore be reduced.

Reducing the rate lowers controller load. Typical practical ranges are:

  • 100 Hz to 500 Hz for many motion systems
  • up to 1 kHz when the application really needs it

Rates outside 100 Hz to 1 kHz are unusual and should only be used when the hardware and application have been checked carefully.

Example:

require ecmccfg "EC_RATE=500"

For startup details, see startup.cmd.

As a rough comparison, common TwinCAT defaults are:

  • 100 Hz for PLC
  • 500 Hz for motion

See host / ecmc server for more host-side guidance.

EPICS PVs update at a lower rate than the EtherCAT master rate. See PV Processing Rate for details.

Global motion commands

The core database provides operational commands for all configured axes:

  • $(P)MCU-StopAll: request a controlled stop while keeping axes enabled.
  • $(P)MCU-DisableAll: stop and disable every configured axis.
  • $(P)MCU-ErrRst: reset all ecmc errors.

The records share the existing ecmc.error.reset global command parameter. Its command bits are reset errors (1), stop all (2), and stop/disable all (4). Stop and disable requests are queued atomically and consumed by the realtime thread. The mbbo command records use Idle and their named command state; writing the command state again retriggers the action.

These PVs are operational controls. They are not safety-rated and do not replace an emergency stop or hardware STO.

Host setup

  • If possible, make sure the native igb EtherCAT driver is used.

For more information, see: