Some time ago I found FabGL, which is a fantastic library implementing a VGA controller and a PS/2 keyboard controller for the ESP32. It means you can use Arduino IDE to create a sketch that talks directly to a real VGA display and a real PS/2 keyboard. For VGA, Red, Green and Blue signals and … Continue reading A portable CP/M machine
My CZ80 computer design requires a dual-ported RAM between the Z80 and the MC6847, to solve the memory contention problem. Now that the RAMs have arrived, I modified the MC6847 test circuit to try them out. The MC6847 was set to text mode. I removed the EEPROM from the circuit and replaced it with the … Continue reading A dual-ported RAM for the MC6847
With a working MC6847 circuit, the CZ80 computer now has a viable video output option. But before tackling the hardware, I would like to test the concept in software, that is, build an emulated CZ80. I grabbed the NASCOM Basic Z80 source code I got from the internet and adapted it to my purposes: added … Continue reading CZ80: emulation
This guide shows how I prepared the rotating earth image for use in the MC6847 test circuit. Basic knowledge of Blender, Gimp and C Programming Language is required to properly follow the instructions.
For this MC6847 graphic test, I chose mode CG1 (see table below). GM0, GM1 and GM2 must be 0, INV, INT/EXT and A/S are "don't care", and A/G must be 1. This mode uses two bits for pixel color, so one byte stores four pixels. The total space required to store one screen is then … Continue reading MC6847 test circuit (part 4)