Yamaha Serial I/O Unit
This page was last modified 14:18, 13 January 2022 by Mars2000you. Based on work by Gdx.


This interface was delivered with the Yamaha YIS-503IIR КУВТ computer for schools of the Soviet Union. This is a module placed in the module slot.

It is based on the RS-232C protocol with extra features (UART i8251 + i8253) and contains a 8kB ROM with a version of RS-232C BASIC that modifies the contents of the function keys (see Yamaha YIS-503IIR for details).

It has 2 serial port connectors and a switch allowing the machine to work in teacher mode or in student mode.

Note: The Yamaha YIS-503IIIR and YIS-805/128R2 КУВТ 2 computers were delivered with the second version of this interface. Both communication systems are completely incompatible.


Yamaha Serial I/O Unit PCB
Yamaha Serial I/O Unit PCB underside
Yamaha YIS-503IIR left side