Not so recently I’ve come around a bunch of Intel 8085 CPUs (actually SIEMENS clones) and decided to put them to work. As you can see on the pic above there is already some work done but I will document the project when more work is one.
A few decisions were made before starting the project. I will be using KiCAD as the EDA suite since I want to learn how to use this free tool and move away from not-very-legal copies of other proprietary EDA tools. This would be my first ever “serious” project using KiCAD. Another decision has been to provide the puny i8085 CPU with most of the following peripherals:
- Two serial ports (with RS232 and/or USB interfaces)
- 8 or more general purpose inputs
- 8 or more general purpose outputs
- An LCD screen (those 128x64 GLCD with parallel bus)
- Some form of storage (Serial EEPROM? SD card? Floppy?)
- A DMA controller
None of those peripherals are particularly strange with maybe the exception of the DMA controller. Feature I plan on having since the i8085 is no processing beast, so offloading all the memory/memory or IO/memory operations from it may allow me to do more impressive stuff with the CPU. Even if in a sense it would be considered cheating.
Another decision that has already been made is separating the most basic CPU and memory circuitry from the IO into two different boards. This way I can in a future change all the IO peripherals without having to redesign and re route the CPU and memory circuitry.
As a target, it would be fun to connect this 1975 CPU to the internet. Making maybe Internet’s most outdated web server.