Xilinx field programmable controllers combine the power of the 32-bit MicroBlaze soft processor cores with the versatility of Spartan-IIE FPGAs to deliver the greatest number of I/Os for low-cost processing solutions.

Staying ahead of the competition is getting tougher everyday. Cost pressures, changing standards, and device obsolescence are just a few of the challenges. To maintain leadership, you need a low-cost, competitive processing solution that’s customizable throughout the entire design cycle and can quickly be brought into high-volume production.

The Xilinx field programmable controller (FPC) solution allows you to create low-cost, customized processors with the peripherals, memory, and logic you want – all on a single, cost-optimized Spartan™-IIE FPGA. With the flexibility to allow integration of other intellectual property (IP) cores on the FPGA fabric, the Spartan-IIE family presents an ideal embedded solution.

Traditional Design Issues

The introduction of embedded soft processors has offered substantial benefits to the world of digital electronics. The industry’s huge appetite for increasingly intelligent and sophisticated control systems has dictated the rapid advancement of processor technology. Perhaps most prevalent of all is the huge leap in demand for embedded microcontrollers and microprocessors.

If you are using a traditional microcontroller unit (MCU) or microprocessor unit (MPU) in your application, selecting the proper device is one of the most critical decisions that will ultimately determine the success or failure of your design. Typically, you must address a number of issues, including:

• Is the MCU or MPU affordable? Does it minimize the overall cost of the system while still fulfilling the design specification?
• Does the unit have the required number of I/Os? Too few can’t do the job; too many can lead to excessive cost.
• Does the device have all the required peripherals? Can you add your own? Does the unit include peripherals you don’t need?
• Are you paying for unneeded IP?
• Will the MCU or MPU be available over the long term? Will the processor become obsolete?

The FPC Solution

Using the 32-bit MicroBlaze™ soft processor core in the Spartan-IIE FPGA, the FPC offers a true low-cost solution for real-time processor control. The combination of a high-performance soft processor and a low-cost FPGA enables you to rapidly develop programmable systems for cost-sensitive applications.

The enhanced integration of embedded applications means fewer interface issues, and processor-based designs developed in the FPGA can more easily be updated without changing the PC board.

Spartan-IIE FPGAs
The Spartan-IIE 1.8V family of FPGAs achieves high-performance, low-cost operation through advanced architecture and the latest semiconductor technology. The seven-member family (see “Spartan-IIE Family Grows” in this issue) offers densities ranging from 50,000 to 600,000 system gates. Spartan-IIE devices also provide system clock rates beyond 200 MHz.

The Spartan-IIE FPGAs have a flexible, programmable architecture of configurable logic blocks (CLBs), surrounded by a perimeter of programmable input/output blocks (IOBs). There are four delay-locked loops (DLLs), one at each corner of the die. Two columns of block RAM lie on opposite sides of the die, between the CLBs and the IOB columns. The XC2S400E has four columns and the XC2S600E has six columns of block RAM. A powerful hierarchy of versatile routing channels interconnects these functional elements. Figure 1 shows a block diagram of a Spartan-IIE FPGA device.

This flexible platform is an ideal base for implementing a controller system. An embedded microcontroller takes the concept of integration one stage further by permitting you to embed the controller system into a small section of a programmable device. No longer does the microcontroller have to exist in a standalone package; it can now be embedded deep within custom hardware.

Spartan-IIE FPGAs are customized by loading configuration data into internal static memory cells while permitting unlimited reprogramming cycles to become a viable upgrade path for future product enhancements. Therefore, Spartan-IIE FPGAs are ideal for shortening product development cycles while offering a cost-effective solution for high-volume production.

In addition, the Spartan-IIE family delivers a cost-effective platform with high numbers of I/Os to provide excellent I/O expansion (up to 514 user I/Os). Table 1 compares the number of I/Os in two traditional microcontrollers against the number of I/Os delivered by two Spartan-IIE FPGAs.

MicroBlaze Soft Processor
The MicroBlaze 32-bit RISC soft processor is a true 32-bit processor, supporting 32-bit bus widths. The core is a RISC-based engine with a 32-bit LUT RAM-based register file with separate instructions for data and memory access.

The MicroBlaze soft processor supports both on-chip block RAM and external memory. All peripherals use the same IBM CoreConnect™ OPB bus as the IBM PowerPC™ processor – which means the processor peripherals are hardware compatible with the PowerPC processors on Virtex-II Pro™ FPGAs.

The MicroBlaze embedded system, including the MicroBlaze core and selected processor peripherals, is shown in Figure 2. Several peripherals are available to support the MicroBlaze processor, including memory controllers, UART, GPIO, I 2 C, 10/100 Ethernet MAC, and many more.

The MicroBlaze core offers the flexibility and scalability of embedded processor programmable logic devices. The MicroBlaze processor requires less than half the logic resources yet offers more than twice the performance of competing soft processors, as measured by industry-standard Dhrystone-MIPS (D-MIPS) benchmarks. Delivering 49 D-MIPS of performance at 75 MHz, the MicroBlaze processor occupies only 1,050 logic cells in the Spartan-IIE FPGA.

FPC Applications
As shown in Figure 3, FPCs have significant applications in the traditional 16- and 32-bit microcon-troller and microprocessor markets, which include automotive, industrial, and high-end consumer applications.

Automotive
The modern automobile is replete with microcontroller-based systems providing automated control for just about every conceivable part of the car. Braking systems use microcontrollers to deliver advanced safety features, such as ABS and traction control. Windshield wipers are controlled to bring us timed interval wipes and even rain-sensitive automatic wiper activation. Heating controls for the vehicle interior monitor multiple zones within the passenger compartment, automatically adjusting the supply of air to maintain the desired temperature. Seats even remember the favored positions for different drivers of the car and readjust themselves automatically.

Industrial
No longer must large workforces be trained to monitor a specific area of a production plant. Today, a series of microcontroller-based monitoring modules, often linked to a central station, replaces these human counterparts. Microcontrollers work tirelessly around the clock without lapses in concentration, requiring only the most minimal maintenance and supervision.

Consumer
Walk into any electronic store and you will find a host of products that use some kind of microcontroller: MP3 players, video recorders, Web tablets, televisions, plasma displays, set-top boxes, refrigerators, washing machines, telephones, answering machines, ovens, toasters, printers, and scanners all offer added functionality through the use of a microprocessor.

The Benefits of FPCs

The Xilinx FPC solution combines the low-cost Spartan-IIE FPGA family with the compact, high-performance MicroBlaze 32-bit RISC processor core. You also get complete embedded system tools (EST) support, including GNU compiler and debugger; hardware and software development tools for implementation, simulation, and verification; and more than 30 fully parameterizable processor IPs. Overall, FPCs offer a low-cost, high-performance, and easy-to-use solution. Among the benefits of FPCs are:

• Reduced costs – By integrating your design onto a single device, you not only save time and effort, you also reduce your overall costs. Spartan-IIE FPGAs are the lowest cost programmable logic devices you can get. They also allow you to integrate costly board-level features such as DLLs, RAM, a variety of I/O translators – as well as MicroBlaze, the industry’s fastest soft processor – into a single, compact, low-cost platform.
• More user I/Os – Spartan-IIE FPGA devices contain as many as 514 user I/Os, with more than 70% additional capacity, and the lowest cost per I/O than competing FPGAs in the same density ranges. This competitive advantage allows you to integrate more features and also shrink the form factor for each device.
• Customization – You can create a customized controller and peripheral set to meet your exact and evolving design requirements. Unlike other solutions, with FPCs you are no longer locked into a rigid, preselected set of peripherals – or have to pay for unused function sets. In addition, Xilinx offers more than 30 processor IPs to choose from.
• No obsolescence – Xilinx allows you to purchase the MicroBlaze soft processor core source code. This option guarantees product availability for any application you choose. You can also port the core across Xilinx product lines – even target an ASIC device.

Conclusion

FPCs from Xilinx deliver the highest I/O for low-cost processing solutions. They create a customized controller and peripheral sets to meet your exact – and evolving – design requirements. Freed from a fixed set of peripherals, you now have the power to custom tailor your peripheral set to meet your needs. In addition, the opportunity to purchase the MicroBlaze structural VHDL source code assures you of product availability well into the future. FPCs reduce your overall design cost and inventory while bringing you the highest performance from your logic devices.

For more information on the FPC solution, visit www.xilinx.com/fpc/.

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