FPGABee Version 2 - Premium 128K HDD
FPGAbee version 2 came about once I realized that I'd taken a slightly wrong path with the first version. I'd originally planned to emulate much of the disk functionality in software but came to realize this made it just another emulation project. The point of this was to learn about hardware.
So after some careful thought I set aside most of the second CPU/console mode/PCU functionality and reverted to the plain Microbee core. From there I decided to target a Microbee Premium 128K with hard disk. I chose the hard disk model because it's more convenient to use and the disk controller is actually simpler to implement.
- 128K RAM including all the port 50h paging modes.
- Supports all the relevant 6545 CRTC registers including character and screen dimensions, base address etc...
- Colour video - 2K colour RAM
- Extended PCG graphics - 16K PCG RAM, 2K attribute RAM
- WD1002 disk controller for HDD and FDD access.
- Reads virtual disk images from SD card formatted with a custom file system format.
- fbfs tool for manipulating SD disk images.
- New simpler PCU (Peripheral Control Unit) implemented by hijacking the Microbee's Z80 processor via non-maskable interrupt (NMI). In other words, no second processor is necessary.
- Could easily be extended to 1Mb RAM and 32K PCG RAM (as per Premium Plus spec).
Building Version 2
Note: This whole section is a work in progress and I'm actually retro-writing these articles after the fact.
- Building FPGABee V2 - ROM in RAM
- Building FPGABee v2 - Better Aspect Ratio
- Building FPGABee v2 - PCU Firmware Working
- Building FPGABee v2 - PCU Supporting Hardware
- Building FPGABee v2 - Hijacking the Z80
- Building FPGABee v2 - FBFS File System
- Building FPGABee v2 - Testing and Fixes
- Building FPGABee v2 - First Boot
- Building FPGABee v2 - Disk Controller
- Building FPGABee v2 - Disk Geometry
- Building FPGABee v2 - More RAM!
- Building FPGABee v2 - Colour and Extended PCG Graphics
- Building FPGABee v2 - Screen Geometry
- Building FPGABee v2 - Change of Plans