Hot Connect and Device ID on the iC92xx controller

Version Number	Description
1.0	Initial version

This application presents how to use the Hot Connect (HC) feature with sub devices on the ECAT network and the benefit of using Hot Connect.

1. Supported Components

Component Name	Version
iC9200 series	≥ 2024.3
iCube Engineer	≥ 2024.3

2. Solution details

The EtherCAT implementation on the iC9200 controllers offers many customization features, and one such feature is Hot Connect. Hot Connect allows for a few unique options for the EtherCAT network.

What is Hot Connect

Connected devices supporting Hot Connect can:

Be included in Plant configuration, but not be present at start up

Allow devices to go offline without EC_Topology_OK going false.
Plug in devices while the controller is operational and bringing the newly plugged in device to operational state on the network.

Additionally with iCube Engineer, with Hot Connect activated, the position topology of every device which supports identification is "floating". This allows devices to be connected in an order that does not reflect their position in the Plant tree within iCube Engineer.

Important Terms:

Station Address - An alias assigned in application code. (Generally not required to match HCGroupID)
Identification Value - The ID of the device based on the device's preferred identification mode. (Can be a physical switch setting on certain devices or a programmable register for some other devices) .
Hot Connect Group ID (HCGroupID) - Hot Connect ID of the first device in the group.
Physical Switch Setting - The value of the physical dials on the face of Yaskawa devices. This setting could be from the rotary switch setting (servos) or dipswitches (SLIO bus coupler).

When to use Hot Connect

There are many situations where using Hot Connect provides a better experience for a particular application. Some examples are:

Commissioning of machines that are pared down versions of original. It is possible to configure multiple sections of a machine, but only bring online part of the system.
Troubleshooting and testing of segments of a larger machine. Like the first point, the option to run portions of a machine without having an exact match of the topology configured in the PLANT can be beneficial.
Flexibility in the placement of various devices. This is especially true when a machine architecture (device sequence) is not rigidly enforced, but instead multiple stations are interchangeable or cabling is swapped.
Isolation of stations from being brought down by communications issues of an adjacent station. In an environment prone to abrupt disconnects or electrical noise this can be helpful.

Note: Hot Connect does not remove the requirement for all connected devices to be configured in the PLANT. EC_TOPOLOGY_OK = FALSE when there are unconfigured devices connected. This happens whether or not Hot Connect is enabled.

Using Hot Connect

Since Hot Connect generally only provides benefits with multiple devices on the EtherCAT (EC) network, that is the first step in this set up process.
Open iCube Engineer, either creating a new project from the template, or loading an existing project. Confirm the IP set in iCube Engineer matches the target controller.
If the EtherCAT devices are not populated under the EtherCAT section of the PLANT, then run an EC Bus Scan, or manually add the devices.
In order to verify if Hot Connect is enabled for the project, a user must open the EtherCAT section under the Plant by double clicking. The general configuration settings for EtherCAT devices are located here.
Under the Master Configuration tab, there are a few options, but the most important is Create HC Group for Slaves, as this is what enables Hot Connect for the EtherCAT devices configured in the PLANT. For projects created from the template project in iCube Engineer, Hot Connect is enabled by default.
Enabling this setting does a couple of things:

Hot Connect is Enabled for ALL devices connected to the EtherCAT network

Each individual EtherCAT device is given an ID, which is used for tracking devices, even when connected order changes.

The ESI file for each device defines what Identification mode is used on that device by default. In the example screen shot below for a Sigma-X servo, Explicit Device ID mode is used to ID the device. User should make sure that the ID specified in the register for the mode matches the ID value set up in the Device/Settings page. In the example below, the Sigma-X servo uses the value in the Explicit Device ID register ((0x0134) which is the value on the rotary switch of the servo. Since the rotary switch setting was at 6, the user has to make sure that the Identification value = 6.
The Hot Connect Group ID is automatically set to be equal to the ID value of the device.
The HotConnect/Position in topology indicates that the device can be anywhere in the network order. (Floating).

Note: Currently, since only daisy-chain topology is supported, removing/disconnect the middle device from the chain will disconnect other devices downstream in the network. This poses some limitations on the usage of Hot Connect.

Examples

For the following examples, the same initial configuration and connected topology will be used. Any deviations will be compared against this.

Hardware Configuration in Project Node (listed in Configured order):

CoE Bus Coupler
Servo Drive (Sigma-7)
Servo Drive (Sigma-X)

Actual Initial Hardware Connection (Listed in Connected Order)

CoE Bus Coupler
Servo Drive (Sigma-7)
Servo Drive (Sigma-X)

Disconnecting with Hot Connect disabled

With HotConnect disabled , the configuration in the project must match the configuration on the EtherCAT network connected to the iC9200 controller exactly.

If Hot Connect is disabled, and the Project Node with this configuration is written to the controller, the EC_TOPOLOGY_OK = TRUE, and all the devices under Online Functions will be in OP.

TheEtherCAT network is functional and all sub devices are operational. Motion should be possible on both axes connected to the two servos in this example.

If the last device (in this case AXIS2) is disconnected from the EtherCAT network, the topology changes. EC_TOPOLOGY_OK = FALSE, as the Configured and Connected device orders no longer align.

Current Hardware Connection (Listed in Connected Order)

EC Bus Coupler
Servo Drive (Sigma-7)

In such a scenario, with EC_TOPOLOGY_OK = FALSE, it may be possible to use the device that gets to an OP state. In the example shown below, The MC_Power2 block throws an Error = 4414 since that device is not in the physical network anymore. It was however possible to use Axis1 which is connected to Servo Drive (Sigma-7) which was on the network and reached OP status. (Shown below)

Disconnecting with Hot Connect enabled

If Hot Connect is enabled and the device identification values match the settings on the devices (registers), and the Project Node with this configuration is written to the controller, the EC_TOPOLOGY_OK = TRUE, and all the devices under Online Functions will be in OP.

Disconnecting the last device results in an Error #4414 on MC_Power2. Y_AX_Jog2 generates the error indicating that the servo is not connected to the network.

Once the AXIS2 drive is reconnected, the error still persists. This fixes the physical connection, but has not re-established the EC communication with the drive.

To recover from this state, perform an MC_Reset on AXIS2. Once this completes, MC_Power2.Error goes FALSE, as the drive has re-established communication (this doesn't happen on its own, and if the MC_Reset is not performed, the drive will remain alarmed out with A.A12).

After Toggling JOG_FW, the Y_AX_Jog2 block goes back to commanding motion. The motor for AXIS2 begins to spin again, as if the issue never happened. If the blocks had different variables as inputs, there would be no impact to AXIS1 while trying to recover AXIS2 from disconnect.

Reordering Devices with Hot Connect enabled

With Hot Connect enabled, there is no requirement to connect the devices in the order that they are configured in the PLANT. This is one of the many strengths of Hot Connect as mentioned above.

In this scenario, it is possible to swap the order of the two Servos, and the functionality of the program is maintained. The axis variables continue to correctly correlate to the intended motors, resulting in motion on the expected axes, regardless of the physical order.

Without Hot Connect, either one of two things would happen: Both AXIS1 & AXIS2 would fail to enable, or (and this only applies if both axes are the same model/version) they may move incorrectly based on the motion commanded of the other. Neither of these behaviors is ideal, so if re-ordering devices is necessary, Hot Connect becomes very important.

Swapped Hardware Connection (Listed in Connected Order)

EC Bus Coupler
Servo Drive (Sigma-X)
Servo Drive (Sigma-7)

As shown in here from Online Functions, all the devices are reporting proper status. Motion also is possible, and correctly follows the axis number, not the order of connection.

$graph_of_EC_hotconnect_order_swapped_v1-1.png$

Missing Devices with Hot Connect enabled

With Hot Connect enabled, devices can be skipped or left out from connection, even if they are configured. EC_TOPOLOGY_OK remains true, and the devices on the EtherCAT network remain operational.

$graph_of_EC_hotconnect_missing_v1-1.png$