Acromag is a multi-million dollar international corporation and a leading designer of analog and digital I/O and control products for the industrial market. One of Acromag's newest products is EtherStax™ - ruggedized networked high-speed Ethernet I/O blocks that interface many analog and discrete signals to a control system. The devices serve many industries, including: power generation and distribution; water and wastewater; oil and gas refining; food, dairy, and beverage; chemical and petrochemical; metals processing; pharmaceutical; and military and aerospace. EtherStax I/O blocks are ideal for supervisory control and data acquisition (SCADA) applications at remote sites, for discrete manufacturing, especially automated operations such as machining, assembly, and packaging, and to make OEM machinery "Internet ready."

Acromag EtherStax I/O

Other versions of Acromag's Ethernet I/O products feature fewer channels with 8-bit microprocessors. As Acromag's new product line would combine 10/100 Ethernet with much higher channel density and high-speed I/O, the company wanted to use a signal processor. Acromag found that the Blackfin® ADSP-BF537 processor from Analog Devices, Inc. (ADI) "fit the bill very well." The processor could handle 10/100 Ethernet reliably with processing power left to spare for other tasks, and it was reasonably priced. The fact that the Blackfin ADSP-BF537 processor drew an extremely low current was another selling point. Acromag is a long-time user of ADI components, with analog-to-digital (A-D) and digital-to-analog (D-A) converters in virtually every product.

Switched Ethernet: How it Works

Acromag's EtherStax I/O Products
EtherStax I/O comes in a variety of models that offer a mix of analog and discrete I/O interfaces with up to 96 channels on a single unit. The units can be stacked on top of each other, interlocking for security. The device supports two communication protocols: Ethernet Modbus UDP/IP and TCP/IP with Acromag's i2o® technology for optional peer-to-peer communication.

The unit can connect directly to a host PC with a Network Interface Card installed (NIC). The dual switch ports allow units to be conveniently cascaded, extending network distances, without consuming an additional host port. If the unit is instead connected using the principle of switched Ethernet, connecting one Ethernet device per switch port, then CSMA/CD (described in the sidebar) is suppressed. This increases determinism and bandwidth, as no collisions are possible and the segment may run full speed at full-duplex, ideal for critical distributed I/O and SCADA applications.

The dual network ports may also function as a traditional repeater, providing low-latency network packet transmission that reduces jitter on the network. Units also allow for media redundancy, right to the EtherStax, when used with a redundant switch. The switch will automatically sense the redundant path to the unit and temporarily disable it. If the primary path should later fail, the switch will reactivate the redundant path to the EtherStax, providing media failover protection. This is a key feature for critical SCADA and distributed I/O applications.

The Blackfin ADSP-BF537 processor controls all of the traffic on the switch through its built-in Fast Ethernet Medium Access Controller (MAC), which supports 10-BaseT and 100BaseT operations. The 10/100 Ethernet MAC includes an MII interface - a standard connection to external PHY devices - enabling the Blackfin ADSP-BF537 processor to directly connect to a network. The 10/100 Ethernet MAC peripheral is fully compliant to the IEEE 802.3-2002 standard, and it provides programmable features designed to minimize supervision, bus utilization, or message processing by the rest of the processor.

High Performance/Low Power
Another reason Acromag chose the Blackfin ADSP-BF537 processor was for its high performance. At 600 MHz, and with 132K Bytes of on-chip memory, the Blackfin ADSP-BF537 adds another high-performance member to the Blackfin family. It combines a MAC controller with a state-of-the-art signal-processing engine, and the advantage of a clean, orthogonal RISC-like microprocessor instruction set with single-instruction, multiple-data (SIMD) multimedia capabilities and a single instruction-set architecture. This eliminates the need for separate digital signal and control processors, reducing bill of material costs and greatly simplifying hardware and software design tasks for Acromag.

Acromag said Blackfin's low power design was also of real value. They were able to add another feature to the product because it gave them extra supply capacity. Blackfin processors are designed with a low power and low voltage design methodology and feature on-chip Dynamic Power Management, which is the ability to vary both the voltage and frequency of operation to lower overall power consumption.


Blackfin: SoC for Network-Connected Apps
The Blackfin ADSP-BF537 processor is a highly integrated system-on-a-chip solution for embedded network-connected applications such as Acromag's. It combines industry-standard interfaces with a high-performance signal-processing core, enabling users to develop cost-effective solutions quickly without the need for costly external components. System peripherals include: an IEEE-compliant 802.3 10/100 Ethernet MAC, a CAN 2.0B controller, a TWI controller, two UART ports, an SPI port, two serial ports (SPORTs), nine general-purpose 32-bit timers (eight with PWM capability), a real-time clock, a watchdog timer, and a parallel peripheral interface (PPI). This is augmented by the system expansion capabilities of the part.

In their first model, Acromag is using the Blackfin ADSP-BF537 as an SPI master, controlling the field I/O on the EtherStax I/O device. The processor's SPI-compatible port and seven SPI chip select output pins enable the processor to communicate with multiple SPI-compatible devices. The SPI interface uses three pins for transferring data: two data pins (Master Output-Slave Input, and Master Input-Slave Output). An SPI chip select input pin also lets other SPI devices select the processor. The SPI select pins are reconfigured programmable flag pins. Using these pins, the SPI port provides a full-duplex, synchronous serial interface, which supports both master/slave modes and multi-master environments.

The Blackfin ADSP-BF537 processor contains dedicated network communication modules and high-speed serial and parallel ports, and an interrupt controller for flexible management of interrupts from the on-chip peripherals or external sources and power management control functions. All of the peripherals, except for general-purpose I/O, CAN, TWI, real-time clock, and timers, are supported by a flexible DMA structure. There are also separate memory DMA channels dedicated to data transfers between the processor's various memory spaces, including external SDRAM and asynchronous memory. Multiple on-chip busses running at up to 133 MHz provide enough bandwidth to keep the processor core running along with activity on all of the on-chip and external peripherals. The processor also includes an on-chip voltage regulator.

Blackfin Easy to Program/Lay Out
Acromag developers credited much of their success to ADI's EZ-KIT Lite Evaluation System, a low-cost hardware platform that includes a Blackfin processor surrounded by several other devices such as audio codecs, video encoders, video decoders, flash, SDRAM, and more.

EZ-KIT Lite evaluation systems include a serial number that when registered, yield a full VisualDSP++ integrated development and debugging environment (IDDE) license for 90 days from the date of installation. Acromag incorporated a third-party TCP/IP stack into the Visual DSP++ package. Acromag said the Blackfin processor was very easy to program.

Each EZ-KIT Lite board also includes an on-board JTAG emulator for use with high-performance JTAG emulators available from ADI. These allow developers to set breakpoints, single step through code, view memory, fill/dump memory, perform real-time data manipulation, profile execution and memory access, plot data, and use standard I/O.

To facilitate the design and layout process, Acromag purchased the 208-Ball Sparse MiniBGA package from ADI, making it very easy to route and wire connections.

Acromag developers are now well versed in ADI products, with solid designs for its latest Ethernet products. The company is sold on ADI and Blackfin, and is already planning future products that will include Blackfin ADSP-BF536 and ADSP-BF537 processors.

Arrow Electronics and ADI
The sale at Acromag was made in conjunction with Arrow Electronics, a major global provider of products, services, and solutions to industrial and commercial users of electronic components and computer products. Headquartered in Melville, New York, Arrow is a supply channel partner for ADI and services more than 130,000 original equipment manufacturers, contract manufacturers, and commercial customers.

For more information about Acromag, please visit Acromag.

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