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)
The MC1372 modulator chip has finally arrived, so I can test the MC6847 in full color. The only problem is that it requires completely different clock and amplifier circuits. I decided to follow the schematics and information detailed on the MC6847 datasheet as much as possible, but had to replace some unusual resistor values with … Continue reading MC6847 test circuit (part 3)
Since I have a working display setup, why not extend it a bit to show all the characters supported by the MC6847 ? And with the right wiring on the A/S pin , I could also display all the semi graphics blocks. The address bus lines DA0-DA12 work like a binary counter: depending on the … Continue reading MC6847 test circuit (part 2)
The MC6847 is a video display generator used in some 8-bit computers from the 80's. It was the IC responsible for that ugly characteristic black text over green background of the TRS Color Computer. Since I had a few of these laying around, I decided to evaluate them as a video card processor for my … Continue reading MC6847 test circuit