Abstract: In a keyboard emulation system of the invention, a keyboard emulation circuit is inserted beteen two microprocessors. The keyboard emulation circuit generates a signal for sequentially scanning a key switch matrix constituting a keyboard unit. The keyboard emulation circuit has a keyboard controller of a matrix scan type for generating a key input code by a return signal, a register for setting a key input code by a master microprocessor, and a comparator for receiving an output from the register and a scan signal for comparing them. The master processor emulates a keyboard interface of the slave processor and performs a key input to the slave processor by the keyboard connected to the master processor.

Abstract: A display system with a single character generator is provided with a CRT controller. A raster address produced from the CRT controller and a raster address inverted by a raster address converting circuit are applied to a multiplexer. The multiplexer is further supplied with the most significant bit of a refresh memory address. Depending on the logical state of the most significant bit, the multiplexer selects the raster address or an inverted raster address outputted from the CRT controller 44 and supplies the selected address to the character generator. Display pattern information outputted from the character generator is applied to a bidirectional shift register. Depending on the logical state of the most significant bit of the refresh memory address, the display pattern information is shifted to the right or to the left. The output of the bidirectional shift register 43 is displayed on the CRT 22 and is supplied to station #1 or station #2 by a mirror reflection.