For my senior project in Electrical Engineering at the University of Florida, I decided to get to know my 2068 a little better. I started dreaming up useful ideas that my instructor would think would be hard enough to be worthwhile to spend a whole semester on designing. There are dozens of things to build to add on to it, but after looking at the possibilities, I decided on an unusual idea after seeing a $12,000 logic analyzer by Hewlett-Packard. I was going to build a logic analyzer controlled by my 2068.
My first thought was to memory map the incoming data, which I had done before with my ZX81, but I realized that there was not any free memory to ‘map’ to. Then I remembered the IN and OUT commands that grace the new keyboard, and started researching this scheme.
I found the IN and OUT commands to work very well and was able to take a 2K memory chip (the popular 6116 2K x 8 static RAM), clock it at 8 mhz while reading in the desired data, slowly read it into the 2068 which takes the data and converts it to high and low marks (as shown below) and displays it on the screen and prints it out on the printer.
With this, you can tell when what happens with respect to data control lines, memory addressing, and other logic functions. The timing diagram of an arbitrary set of addresses in the 2068 are shown below. The vertical marks are 125 micro seconds apart, which is the resolution of the analyzer (1/8 mhz).