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VIRTEX PROTO BOARD

by Ingo Cyliax

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The VW-300 also has several clocking options. It has two Dallas Semiconductor DS1073 econo-oscillators (100 MHz and 66 MHz). These can be set up to divide the oscillator frequency by two, which is the default. In addition to these oscillators, the board has a Cypress ICD2053B adjustable oscillator, which can be programmed using a serial protocol either from the FPGA or externally. By default, this oscillator runs at 16 MHz. As if this isnýt enough, there is also an extra oscillator site where you can install your own oscillator module.

Another neat feature is the temperature sensor module. This is a Max1617 die temperature sensor. The Virtex provides a diode-based die temperature output that works with this sensor module. The module converts the temperature reading and lets you read the temperature through a SMBUS interface, either by the FPGA or externally.

Measuring the die temperature is useful for several reasons. Because FPGAs are user programmable, computing power consumption (and power dissipation) is complex. During system testing, you can use the die temperature, and by knowing the ambient air temperature as well as heat transfer coefficients for the package and current air humidity, you can estimate the power consumption and power dissipation.

Also, because this type of Virtex has so many flip-flops and internal tristate buffers, which can cause fights if not properly designed, you can actually overheat the chip at normal operating temperatures. A temperature sensor can be used to detect these conditions and shutdown the chip if the temperature exceeds safe levels. I suppose a boring application of a temperature sensor might be to drive a variable speed fan to cool the chip optimally.

If youýre building systems on a chip, you might want to use serial communication channels to talk with other computers or a terminal. This board includes a TTL to RS-232 level adapter and a DE-9 connector to perform this. For example, this project uses an RS-232 port for a background debugger type interface.

Building a UART in FPGA is not hard. I used to teach students in undergraduate hardware labs to do this. Iýll cover designing UARTs in a later article.

If you like switches and lights, it has those as well. There is an 8-position DIP switch and eight surface-mount LEDs you can read and light up with the FPGA. There are also four pushbutton switches. However, the neatest peripheral on this board is the Infineon IPD2133 8-character 5 ý 7 dot matrix aphanumeric display.

To the FPGA, the display looks like a small SRAM device. There is an address bus and a data bus. The simplest way to use it is to address one of the eight digits (address 0ý7) and write a 7-bit ASCII code to it. The chip converts the ASCII code using an internal character ROM and displays it on the 5 ý 7 array for that digit. Not bad. Figure 2 shows a block diagram of the internal display.

Figure 2ýThe internal display has an address bus and data bus and provides you with many options for use.

You can use this display to show a hexadecimal representation of internal registers, assuming you add logic to your design to use the display. You can also use it to provide a small scrolling text console for your project.

Besides onboard peripherals, there are a variety of headers and connectors that can be used to interface external modules, devices, and logic analyzer inputs to the Virtex on this board. In particular, there are several mezzanine connectors for third party CODEC modules from Insight, as well as A/D and D/A Omnibus modules from Innovative Integration. All of the I/Os are documented in the user manual, and pin configuration files for the FPGA can be downloaded from VCCýs web site.

There are several configurations that are supported on this board for the Virtex chip. I already mentioned the flash PROM for doing SelectMAP configuration, and there are jumpers and headers for serial PROM, JTAG, Xchecker, and MultiLINX configuration. The manual, schematics, and datasheet for some of the components are available on the web site. After you have registered for your board, everything youýd expect from a prototyping board opens up to you.

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