In previous articles, we introduced the IO-Link protocol and its interfaces [What is the IO-Link protocol? How are its interfaces defined?]. Today, we'll delve deeper into the IO-Link system.
We know that the IO-Link system consists of three parts:
1) IO-Link Master;
2) IO-Link devices (IO-LinkDevices);
3) IO-Link cables;
IO-Link devices include field sensors and actuators; IO-Link cables are standard 3-core or 5-core cables; the IO-Link main unit has one or more IO-Link interfaces, and each IO-Link device is connected to an IO-Link interface via a cable (the IO-Link system is a point-to-point communication system).
The IO-Link system overview diagram is as follows:
Upon initial power-up, IO-Link devices are always in SIO mode. SIO mode, also known as "Standard I/O mode," treats the device's IO-Link interface as a standard digital input/output channel.
Each IO-Link interface managed by the IO-Link controller can be configured via software (S7-PCT) to either standard digital input (DI)/standard digital output (DO) mode or IO-Link communication mode.
When the IO-Link Master's port is configured as a standard digital input or standard digital output, it can be used like a regular digital input/output module. When the IO-Link Master's port is configured as an IO-Link Communication port, the IO-Link Master will attempt to connect to the IO device connected to that port.
In IO-Link communication mode, the IO-Link supervisor sends a predefined signal and waits for a response from the IO-Link device.
First, the IO-Link supervisor sends a signal at the highest baud rate. If there is no response, it will continue to send a signal at a lower baud rate. For IO-Link devices, the communication baud rate is already determined. When the device receives a request signal from the IO-Link supervisor, it will respond to the IO-Link supervisor, and the two parties will establish communication. This process is called IO-Link device wakeup.
When an IO-Link device is woken up, the IO-Link supervisor and the IO-Link device first exchange communication parameters, and then begin periodic data exchange.
An IO-Link system can exchange three types of data:
1) Periodic process data (process input/output);
2) Equipment parameters;
3) Events (non-periodic data);
The IO-Link Device Description (IODD) contains complete information about the IO-Link device. Using the IO-Link configuration tools S7-PCT and IODD, devices connected to the IO-Link manager can be configured.
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