Just by chance a found the datasheet and manual of an Montorola 6845 video controller chip. A little later I saw an ad of a video monitor controller board, the ZRT-80, based on this chip. Complete with serial I/F and expandable video RAM and ROM. This was my last Z80 based project and I used it mainly to fiddle with screen resolutions, character maps, display resolutions, downloadable character codes etc. It was the perfect companion to the SB-180 because this one had only serial I/Fs, but no built in video/keyboard port.