IO-Link Transceiver E981.10 from ELMOS ensures better efficiency

In industrial automation technology, sensors and actuators are still mostly connected to the control via switching 24 V or standard analog signals. This is a laborious and unnecessarily expensive procedure, especially considering that in the meantime there are significantly more efficient and space-saving solutions such as, for example, the IO-Link Transceiver E981.10 from ELMOS. With the help of this highly integrated IC, process, parameter and diagnostic data can be securely transmitted digitally coded via a single 3-wire connection and a transmission speed of up to 230.4 kbit/s. What is more, the innovative communications component enables bi-directional communication with I/O field devices. It is therefore high time to think about a technology change. Would you not agree?

Today, for those that want to successfully overcome the permanent balancing act between cost reduction on the one side and higher equipment availability on the other side is, in automation technology, dependent on effective diagnostic concepts and efficient handling of parameter data. Modern sensors and actuators establish the necessary conditions for this. However, so far, it was not possible to efficiently implement their connection to the whole automation system. For some time now, IO-Link - as innovative interface for the ‘last meters’ - offers here completely new possibilities to the process.

In comparison to bus connections of traditional fieldbus systems, with IO-Link it is about a parallel wiring, whereby data rates of up to 230.4 kbit/s can be transmitted over a maximum cable length of 20 m. The signal transmission takes place by means of 24 V pulse modulation and a standard UART protocol. IO-Link uses the standardized unshielded 3-wire connection cable (M12, M8, M5), which is also used for connection of conventional Standard IO (SIO) sensors/actuators. This not only reduces the additional wiring effort to an absolute minimum, but also protects investments already made since proven topologies can be further used and must not be changed.

A further advantage of IO Link: Expensive shielded cable can be dispensed with due to the elimination of analog measurement value transmission. The bidirectional IO-Link communication puts the overriding automation system in a position both to write parameter and configuration data in the sensor/actuator and to read process and diagnostics data from the sensor/actuator. However, IO-Link can also handle communication via binary switching states as used by conventional SIO sensors. The new communications standard is thus backward compatible, almost without restrictions, and can be applied freely combined, also with non IO-Link capable devices.

Due to the open standard, IO-Link can be integrated in all popular automation and fieldbus systems so that a high level of flexibility with regard to supplier selection continues to be maintained. The integration of Profibus, Profinet, Interbus, ASi and EtherCAT are already available and IO-Link integration in the ODVA is being pursued.

However, in order to ensure the requirements for e.g. overcurrent and overvoltage protection, defined in the IO Link specification, a large number of individual components - transistors, diodes and other passive components - are used in the majority of the IO-Link devices available so far. For the first IO-Link field devices, this was so far the only possibility to map the interface to the wire and to fulfill the IO-Link specification. Especially problematic here is the required interoperability with the control side since the corresponding electrical circuits can orient themselves solely to the IO-Link specification.

A remedy for this is the IO-Link Transceiver E981.10, which now offers developers of IO-Link capable sensors/actuators a highly integrated, space-saving solution for the wire interface of their sensors/actuators. The driver component, which is backward compatible to today’s Standard IO applications, fulfills the requirements of all relevant standards and its features include a wide input voltage range from 8 V to 36 V, a high driver capability up to 200 mA, integrated wake-up detection and a data transmission speed of up to 230.4 kbit/s. The driver stage can optionally be used as low-side, high-side or push-pull. Short-circuit, over-current and overtemperature protection functions ensure a high operating safety and also simplify application design.

Thanks to an internal 5 V voltage regulator and a 3.3/5 V compatible digital interface, the E981.10 can be combined with a variety of popular microcontrollers e.g. with a NEC Electronics Europe‘s 78K0R MCU, which in this case takes over protocol implementation. The component is useable with a chip temperature up to +150°C and is provided in a small 4x4 mm QFN package, thus making it ideally suited for use in compact sensors and actuators.

How useful the diverse functions of the E981.10 prove to be in practice is shown in examples including the integrated wake-up detection. In most cases, an IO-Link system consists of an IO-Link master and one or more IO-Link devices i.e. sensors and actuators. The IO-Link master provides the interface to the programmable logic controller (PLC) and controls communication with the IO-Link devices connected.

As a result of the backward compatibility of IO-Link devices to Standard IO (SIO) ports of the higher level control, IO-Link sensors and actuators initially behave like SIO devices. However, it is possible for the IO-Link master to identify IO-Link capable devices in the network and switch over to IO Link communication mode. This takes place by a so-called wake-up signal.

During wake-up, the signal applied to the sensor in SIO mode is overwritten by the master with a typically 80 μs impulse. The signal state can be high or low level, according to the sensor output signal. The information about a wake-up event exists for the software of two bits; from the level to be driven (TXD) and the level to be received (RXD). A combinatorial linkage of two IO ports for generation of an interrupt is generally not available with the microcontroller used. Support of the wake-up procedure by the E981.10 reduces the demands on the software, which otherwise would have to monitor the communication path by comparing the send and receive signal in high resolution. The binary wake-up signal provided by the transmitter can trigger an interrupt, which in turn results in relieving the microcontroller. The signaling of an overcurrent error condition (ILIM signal), caused by a short-circuit or other incidents, is a further example of the high flexibility of the E981.10. This feature contributes to a significant increase in the long-term reliability of the product. By recognizing these errors, the software can react intelligently and deactivate the driver stage. In addition, the power dissipation can be reduced by examining the line for overcurrent in long intervals.

With the qualification and final EMC tests at the renowned test and certification body of the FTZ in Zwickau, Germany, development work of the E981.10 is now complete according to plan. The official test report of the FTZ Zwickau, which proves compliance with the EMC limit values at transmission rates of up to 230.4 kbit/s, is available upon request.

Samples of the E981.10 are now available from Gleichmann Electronics. Large quantities will be available starting March, 2010. We will be pleased to help you in the selection of the optimal microcontroller, whereby corresponding IO-Link protocol stacks are available for almost all of the microcontrollers in our product portfolio. Upon request, we will gladly send you detailed information and product descriptions of the E981.10.