IO-link is an industrial communication interface. Proposed by the Profibus User Organization Committee of the same name ( German: Profibus Nutzerorganization eV , English PROFIBUS User Organization ), the developer of the Profibus family of industrial interfaces. It was subsequently standardized as the international standard IEC 61131-9.
The interface is intended for the intellectualization of discrete sensors, such as, for example, an end sensor or an actuator . Most of these sensors are connected via three wires: two sensor power wires and an on / off signal wire (the so-called dry contact or open collector ). To preserve the existing standards of such discrete devices (for example, the IEC 60947 end sensor standard ), the new interface communicates with the device via a signal circuit. To maintain compatibility, all terminal devices operate in the normal dry contact mode when the power is turned on, switching to communication mode only after the wizard performs a certain procedure.
The purpose of the interface predetermines that the interface cannot be network, but only a point-to-point type, with a master and a terminal device.
Specification
For 2016, there are two versions of the specification: 1.0 and 1.1. They are limited compatible: terminal devices 1.1 can only work with master 1.1.
Physical layer
Supply voltage 24V. The master is required to provide a load current of up to 200mA. High current consumption of the terminal device is allowed using an external power source.
In the discrete input-output (SIO) mode, the output acts as a short circuit to the + 24V power wire, and the input works as a 5..15 mA current limiter minus the power supply.
Signaling in communication mode (SDCI) is based on an asynchronous interface with 8 data bits, a parity bit and one stop. Three speeds are allowed: 4.8, 38.4 and 230 k baud . The terminal device can support one speed, the master finds out the operating speed of the terminal device by enumerating all speeds during initial initialization. Logical β1β is transmitted as zero voltage; logical β0β as + 24V.
To maintain compatibility with existing infrastructure, connectors and cables are mainly derived from IEC 60947-5-2 . The maximum cable length is 20 meters. Valid connectors are M5, M8, or M12.
Protocol
Two states are specified for the interface: SIO and SDCI. SIO - conventional discrete input and output mode in accordance with the purpose of the terminal device. For compatibility with existing equipment, both the master and the terminal device always operate in this mode when the power is turned on. To switch to the data exchange mode ( SDCI ), the master must perform a special procedure (wake-up). The master is also required to determine the hot swap of the terminal device with the appropriate procedures for restoring the desired state of the terminal device.
A request-response protocol, the initiator of any exchange is the master.
See also
- AS-Interface
Links
- www.io-link.com - The official website of the IO-link consortium.
- IO-Link. Physical level.
- IO-Link. Data structure