Building FPGABee Version 1
The first version FPGABee delivered a mostly working clone of a ROM based Microbee - similar to the PC85B model.
Although the original intention was to take it further, I decided to back track and take a different approach with version 2 so some of this information is now obsolete (most notably the console mode and PCU).
- Runs on a Digilent Nexys3 FPGA Development Board
- Uses OpenCore T80 for Z80 CPU
- 32K RAM, 28K ROM, 4K Video RAM/Character ROM\
- Partly functional 6545 CRTC implementation - cursor, keyboard, video generation
- Connects to VGA monitor at 640x480 resolution with the Microbee output (512x256) displayed centered
- Uses PC keyboard with natural character mapping
- Programmable Character Graphics (PCG)
- Cassette Load (Save not implemented yet) from FAT32 formatted SD card
- Console Mode for control over peripheral functions
Getting started with FPGAs and VHDL and just enough ciruitry to boot a Z80 processor and display a blinking LED!
Implementing a VGA video controller and mapping to memory layout matching that of a Microbee.
The 6545 is the heart of the Microbee's video controller. This article looks at how it's implemented in FPGABee, including cursor logic.
Covers connecting to a PS-2 Keyboard and mapping received key events to Microbee key-switches and then making them visible to the Z-80 through the CRTC.
Debugging PCG graphics issues and getting a game I wrote in the 80's working on FPGABee!
Connecting a speaker to the FPGA and getting Microbee sounds out of it.
Implementing a virtual cassette interface and the Peripheral Control Unit as a user-interface to control it.