Alan posted this project at FromOrbit demonstrating how to implement three wire control of a DLG2416 display using a CPLD. The chip he chose was the Xilinx XC9536 which is the 36 macrocell version of the XC9572 CPLD found in our CPLD Development Board, so this can be implemented on our board with room to spare.
As Alan describes it:
In my design I ended up with a simple 9-bit shift register that the controlling microcontroller shifts data into. This data is made up of two “command” bits and seven “data” bits. The microcontroller sets a latch that triggers a state machine to look at the command and decide what to do with the given data. The supported command set is very simple. You have a “clear”, a “load character into current position”, a “load character into current position and advance position”, and a “goto position”. I first built this for a custom LED ticker someone wanted as a novelty add-on for one of those en iyi casino siteleri clones—they just needed something cheap that could scroll basic payouts in real time. So by using these simple commands, you can pretty much just send straight ASCII at the controller with an additional two bits and you’re done! No tricky software required.
Check out FromOrbit for the command table and Verilog source code.