Configuring Fast Start Up (FSU) for Profinet I/O

This topic contains the following sections:

General Information on FSU

In a Profinet network, the Fast Start Up (FSU) function is used to minimize the startup time of a Profinet device and to power up the device quickly. Fast startup times of I/O devices are necessary in, for example, tool changing applications where the robot should be ready and active within a short time after a tool change. With Fast Start Up, the I/O device is operational after power on and connected to the Profinet controller in less than 500 ms (time is defined by the PI (Profibus & Profinet International) Organization). Operational and connected means, the Profinet controller has established a connection to the I/O device and the I/O device can cyclically exchange process data with the controller.

With enabled FSU, the I/O device sends a DCP (Discovery and Configuration Protocol) hello frame to the Profinet controller as soon as power on is completed. When the controller has received the frame, it establishes the connection to the I/O device (see below how to configure the DCP hello service).

The FSU function can only be used if the Profinet controller added to your project supports this function. Whether your Profinet controller supports FSU can be seen in the 'Settings' editor of the 'Profinet' PLANT node. If supported, the editor provides the 'Fast StartUp' category with activated 'DCP hello supported' checkbox (checkbox is read-only).

To use an I/O device with fast startup, the following configuration steps must be carried out:

Step 1: Activate and configure Fast Startup for the I/O device.
Step 2: Configure the port settings on the I/O device. Additionally, if the I/O device is connected via a switch to the Profinet controller, configure the switch.

Configuring FSU for I/O device

Proceed as follows:

Open the 'Settings' editor of the device's Interface node by double-clicking the Interface node in the PLANT. Select the 'Fast StartUp' category on the left.
The 'Fast StartUp' category is only available if the I/O device supports the FSU function and is enabled on the device.
Set the parameter 'Configure FS hello' to 'Yes'. (With 'No', the I/O device does not send DCP hello frames.)
Set the following Fast Startup parameters to configure the DCP hello frames sent by the I/O device in Fast Startup Mode:

Parameter Description

FS Hello Mode Specifies the hello mode to be used.

'OFF' (default setting) - No hello mode used.

'Send DCP_Hello.req on LinkUp' - the I/O device sends the DCP hello frames after LinkUp.

'Send DCP_Hello.req on LinkUp after HelloDelay' - the I/O device sends the DCP hello frames with a delay after LinkUp. The delay is set with the 'Wait time between LinkUp.ind and DCP_Hello.req' parameter (see below).

Wait time between DCP_Hello requests Specifies the time interval in milliseconds between two DCP hello frames sent by the I/O device. Default: 30 ms

Number of retransmissions of DCP_Hello.req Specifies how often the DCP hello frames are resent to the I/O device if no connection to the controller could be established. Value range: 1...15; default: 3

Wait time between LinkUp.ind and DCP_Hello.req Specifies the delay in milliseconds between LinkUp and first DCP hello frame issued by the I/O device. The parameter is only valid if 'FS Hello Mode' is set to 'Send DCP_Hello req. on LinkUp after HelloDelay'. With the setting 'Off', the I/O device sends the first DCP hello frame without delay. Default: Off

Parameter	Description
FS Hello Mode	Specifies the hello mode to be used. 'OFF' (default setting) - No hello mode used. 'Send DCP_Hello.req on LinkUp' - the I/O device sends the DCP hello frames after LinkUp. 'Send DCP_Hello.req on LinkUp after HelloDelay' - the I/O device sends the DCP hello frames with a delay after LinkUp. The delay is set with the 'Wait time between LinkUp.ind and DCP_Hello.req' parameter (see below).
Wait time between DCP_Hello requests	Specifies the time interval in milliseconds between two DCP hello frames sent by the I/O device. Default: 30 ms
Number of retransmissions of DCP_Hello.req	Specifies how often the DCP hello frames are resent to the I/O device if no connection to the controller could be established. Value range: 1...15; default: 3
Wait time between LinkUp.ind and DCP_Hello.req	Specifies the delay in milliseconds between LinkUp and first DCP hello frame issued by the I/O device. The parameter is only valid if 'FS Hello Mode' is set to 'Send DCP_Hello req. on LinkUp after HelloDelay'. With the setting 'Off', the I/O device sends the first DCP hello frame without delay. Default: Off

Configuring the port settings on the I/O device

Proceed as follows:

For any port used for the connection between Profinet controller and I/O device, open the 'Settings' editor of the device's Port node by double-clicking the Port node in the PLANT. Select the 'Fast StartUp' category on the left.

From the 'MAU type' (MAU = Medium Attachment Units) list box select the MAU type used for the port. The MAU type defines the physical settings of the Profinet I/O device. The list box provides only the values supported by the I/O device as per its device description.

Note
According to the Profinet standard, a transmission rate of 100 Mbit/s (100BaseTX), full duplex, is required for all Profinet devices in the network which have the Fast Startup function enabled.

Note
The MAU type setting for all ports using Fast Startup must be identical.

If the I/O device is connected via a switch to the Profinet controller, activate the Fast Startup mode on the port used for the connection to the I/O device. Configure the switch with the same settings as the one set for the I/O device ports.

Note
The port settings must be identical for the I/O device and the switch. To further optimize the startup time, deactivate auto negotiation and auto crossing at the switch.

Further Info
For further details about the Fast Startup function, please refer to the manufacturers' manual provided for the switch.