CoolRunner-ll: Xilinx CPLD Development Kit（2）

Published:2011/7/28 21:53:00 Author:Li xiao na From:SeekIC

By Paul Goossens

The hardware

The printed circuit board comes with a CPLD type XC2C256TQ144-7 fitted ex-factory. If desired, a second CPLD may be fitted on the board — this may be an XC2C64 or an XC2C32. An oscillator running at 1.8432 MHz supplies the clock signal required by the CPLDs. The oscillator module is fitted in an IC socket allowing it to be easily exchanged if a different clock frequency is in order. In your choice of the oscillator module, do bear in mind the pin connections and the supply voltage (3.3 V).

The power supply may be a DC adapter (mains eliminator) or a battery. Depending on your choice, JP1 may have to be relocated. If an external supply greater than 3.3 V is used, the jumper has to be in the ’Int’ position (internal stabilization). When two series-connected 1.5-volt batteries are used, JP1 needs to be moved to the ’Ext’ (external stabilization) position. As shown by the indication, the supply voltage is not stabilized in the second case. If a too high supply voltage is applied, components may be damaged (as we learned the hard way), so be careful!

A 25-way sub-D connector is provided to be able to program CPLDs. This connector is linked to the parallel port on the PC using the cable supplied in the kit. Those of you in possession of another Xilinx JTAG interface may conveniently use the dedicated JTAG connector on the board.

The I/O resources on the board are scanty. One LED and a single pushbutton are connected to the CPLD. Sure, that may be sufficient for a few initial experiments, but the possibilities are of course limited to say the least. Instead of extra I/O, Xilinx have opted for a prototyping area on the board, which allows peripheral hardware to be added quickly and easily. Furthermore, all relevant signals and supply rails are bonded out to pins on four connectors (you have to mount your own 40-way box header, though). These connections are useful if the footprint of your extension circuit exceeds the space offered by the prototyping area.

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