ZX Spectrum - grandfather of the personal computers. Champion form early 80s. 

The ZX Spectrum was a popular 8-bit home computer by Sinclair Research in the 1980s. Even though some of these computers may still work, the audio tapes, the TV with an analog tuner, and the micro-switch joystick that were used with the original ZX Spectrum are outdated and hard to find in good working order or to replicate. 

As many other old closed systems are also very difficult to update to support modern peripherals, there is a necessity to provide a methodology to adapt such systems to support new peripherals while being compatible with existing software. This implementation is a means by which to validate the methodology before applying it to a physical system. 

The work proposed in this paper focused on recreating a ZX Spectrum+/48K computer and interfacing it with modern peripherals on an FPGA. This was accomplished by adding a co-processor to assist with the control of the more complex peripherals. Otherwise, the original system would require complex architectural changes and would perform poorly due to the low performance of the Z80 CPU. 

This work departs from previous works on emulating a ZX Spectrum. It emphasizes the use of different upgraded peripherals together with the use of a NIOS II soft processor as a co-processor to manage the SD card accesses and save-state functionality.

Only after successfully running a diagnostics ROM to check the system health will you be able to play original ZX Spectrum games from an SD card, for games which use a PS/2 keyboard and a pair of joysticks. RW Describe this new implementation.