Well I finally managed to figure this all out, and put together a Full instructional video. This video series that I have put together explains the fundamental concepts and signal requirements for driving the HD44780 LCD display unit using the VHDL hardware description language.
The VHDL code has been compiled to be used with the Altera Cyclone II FPGA on the Altera DE2 development board. However, you can modify the code slightly to port it to other development boards or FPGA’s and CPLD’s.
In the videos I review the signal requirements using actual waveform scans from a Logic Analyzer that show the Control and 8-bit databus signals used to drive the HD44780 display through its initialization sequence and then a character display sequence for printing a custom message onto the LCD screen.
The signals scanned are all generated by a VHDL source file programmed onto an Altera Cyclone II FPGA on the Altera DE2 development board. This VHDL file produces a 32 character message to be displayed on the HD44780 LCD screen.
After reviewing the Waveform scans I briefly go over the VHDL code step by step to explain how it all works.
I will be providing a link to a devoted webpage on my Website for this project where I will provide further images and information and also extra links to other files such as the VHDL code source file for you to download. With this, you can try and create your own custom messages on an FPGA or CPLD board of your choosing.