The birth of this page! As I devise more and more profound circuits, I'll put them here for everyone to see.
Version 1.0 of the 'vga text controller' has been released. This project originated from my attempt to demonstrate a simple monochrome text-display in an FPGA. The demo-files are designed to run on the Xess XS40 FPGA-boards, revision v1.4 or later. I used an XS40-010XL+ v1.4 for development.
On an unrelated note, back in October of last year, I ordered an Avnet Virtex Development Board for work. Like other commercial Xilinx FPGA-boards, the Avnet is programmed with the Xilinx parallel download cable, a $99 piece of plastic + wires from Xilinx. The kit includes one cable, but I wanted to experiment with the board at my home PC without lugging a cable between home and work. Cheapskate that I was, I modified the Xess's XSTOOLs package to program the AVNET board through the Xess XS40's I/O pin-headers. I saved myself $100 cable, but wasted one morning stumbling through a bunch of hierarchical C++ code. The program-hack involved changing the pin-assignments, to remap them to unused XS40 pins. The XSLOAD program uses the slave-serial programming mode (CCLK, PROG, DIN) on Virtex and XC40xx BIT files. With this hack, I can program any Xilinx FPGA-board (Spartan2, Virtex, XC4000x) without having to buy the Xilinx cable. Of course, I didn't use the AVNET board at home beyond the first week, so I am left holding nothing but a program-hack with imaginary usefulness.
With revision v1.0 of the VGA-text controller finished, my next project will be integrating it with Jan Gray's XSOC. XSOC is a simple, RISC CPU design that fits on an XC4005XL (< 5000 logic gates!) With my text-controller's area-requirement at 35% of an 4010XL, I hope to fit both on a single XC4010XL.
What is Verilog?
Verilog is a hardware description language useful for digital circuit design, modeling, and simulation. Verilog competes with VHDL, the hardware description language endorsed by the rest of the world, and the US Department of Defense.
The language syntax uses many constructs and operators familiar to computer programming langauges, like C. Of course, circuit modeling gives rise to constructs to capture hardware concepts, like registers and circuit delay.
VGA-text controller (readme file)
Text-display controller for the Xess-XS40 v1.4. The controller generates (almost) standard VGA signals. The demo connects the Xess's PS/2 connector with a simple PS/2 port capture circuit. The capture circuit writes scancodes into the text screen area.
Two distributions are available :
xs40_text10.zip- Demo files only, no source code
xs40_text10s.zip - full source/schematic code + demo files, requires Xilinx Foundation 2.1i or later (works with Student Edition)
http://www.fpgacpu.org - FPGA CPU architectures, a great site for hardware engineers interested in doing their own CPU-design
http://www.xess.com - Xess's homepage
http://www.verilog.com - Learn about Verilog
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