Tag Archives: RS485 mode

Powering industrial communications with Atmel

Industrial communications are a critical aspect of current-gen automated systems – with defined standards that continue to evolve as new industrial Ethernet protocols emerge. Atmel’s versatile portfolio of microcontrollers (MCUs) provides engineers with the peripherals and internal system architecture required to efficiently interface new products with leading field busses, industrial Ethernet standards and wireless communications.

Field Bus

Atmel offers a dedicated RS485 mode for USART peripherals which is available on most ARM processor-based AT91SAM and AVR 32-bit microcontrollers. Meanwhile, a rich number of DMA channels on Atmel megaAVR, AVR XMEGA, AVR 32-bit and AT91SAM MCUs unload the CPU during industrial communication transfers, with multi-layer bus implementation on Atmel 32-bit microcontrollers enabling true parallel data transfers and effectively minimizing bus load limitation.

In addition, there is an (optional) external bus interface on several Atmel microcontrollers, with up to 32-bit data supports dedicated ASSP for protocols such as Profibus. Plus, up to 12Mbps USART on the SAM3U and SAM9 microcontrollers provides support for external transceivers. In terms of single or dual CAN controllers, select Atmel MCUs are V2.0A and V2.0B standard compliant, supporting independent message objects that are programmable on the fly and ideal for field bus such as CANopen and DeviceNet.

Industrial Ethernet

The vertical integration of management execution systems with factory floor equipment has resulted in the continued convergence of the Ethernet TCP/IP protocol with industrial field busses. As noted above, several industrial Ethernet protocols have emerged, including Profinet, Ethernet/IP, ModbusTCP/IP, EtherCat and Ethernet Powerlink.

“Most industrial Ethernet automated systems do not require compliance with a PLC cycle times lower than a few milliseconds. For these applications, the industrial Ethernet protocol can be cost-effectively implemented in software on a microcontroller with an integrated standard Ethernet MAC peripheral,” an Atmel engineering rep told Bits & Pieces.

“Due to their moderate flash size requirement, protocols like Modbus TCP can be implemented in a microcontroller. Atmel offers ARM-based and 32-bit AVR microcontrollers with up to 512KB of flash and an integrated Ethernet MAC unit.”

According to the rep, one of the most noteworthy features includes a 10/100 Ethernet Media Access Controller (EMAC) peripheral with chained buffer Direct Memory Access (DMA). This acts as a master on the internal multi layer bus with multiple internal SRAM blocks – enabling a true parallel data transfer between the Ethernet frames and the application data.

“Atmel’s  SAM9  MPUs are also price-competitive solutions for implementing industrial Ethernet protocols, such as the Ethernet/IP standard, which requires a higher flash size and faster execution time,” the engineering rep continued.

“Atmel’s  SAM9 MPU, like the SAM9G45, offers a variety of benefits, including a 400Mhz clocked ARM926EJ core with 32KB instruction and data caches speed execution time. There is also deterministic execution time with the use of the TCM (Tightly Coupled Memory) interface, enabling access to the internal SRAM with zero wait state at 400MHz. Indeed, by dynamically configuring the SRAM as TCM, Ethernet frames can be analyzed at full speed without any copy to the cache.”

For motion control applications, synchronism and short latency aspects are crucial. Protocols such as Profinet IRT or Ethercat address these requirements and are suited for systems with a sub-millisecond PLC times. In this case, specific ASSP or FPGA solutions must be used. The Atmel SAM9G45, with its dual EBI feature, lets designers integrate the industrial Ethernet communication module with minimal performance impact. Data transfers between the ASIC or FPGA can be handled by the DMA unit, in parallel with external RAM access.

Wireless Communication

Wireless communication in the industrial automation sector is increasingly popular, as it provides an easier way to install and connect mobile or inaccessible equipment. To be sure, industrial control equipment such as PLC and DCS IO modules primarily utilize IEEE802.11 WLAN and Bluetooth standards. And that is one of the reasons Atmel’s 32-bit microcontrollers and microprocessors feature an embedded multimedia card interface which supports connection to an SDIO WLAN or Bluetooth module. In fact, a full reference design based on the Atmel AVR 32-bit microcontroller and the industrial Wifi Module from H&D is available for evaluation and development here, while a Linux-based solution for Atmel SAM9 microcontrollers can be found here.

And last, but certainly not least, industrial sensors and actuators have demanding requirements for power consumption, board space and implementation cost. For these products, IEEE802.15.4 technology, such as Zigbee or Wireless-HART is most appropriate, with Atmel offering complete wireless solutions based on our low-power microcontrollers and RF transceivers. Benefits include excellent RF performance, which enables longer range and more robust RF link, optimized power consumption and lowest system cost.

Additional information about Atmel MCUs that can be used to power a wide range of industrial communication devices is available here.