Input-output apparatus for a microprocessor

Input-output system for a microprocessor, said microprocessor having a first (17) set of output terminals and a second (16) set of output terminals, said system comprising

• a plurality of first lines (24-29);
• first connecting means (18-23) for connecting each of said plurality of first lines to a respective output terminal of said first set of output terminals;
• a plurality of second lines (31-38) each connected to a respective output terminal of said second set of output terminals;
• a plurality of indicator means (49-56);
• second connecting means (41-48) for connecting each of said indicator means to a respective output terminal of said second set of output terminals and, thereby, to a respective one of said plurality of second lines;
• wherein said microprocessor (1) includes means for imposing a binary signal having a first level on each of said plurality of first lines in turn during a data input time interval and binary signals having a second level on all of said plurality of first lines during a data output time interval substantially exceeding said data input time interval;
• wherein said microprocessor further includes means for imposing an output signal at each output terminal of said second set of output terminals only during said data output time interval;
• and further comprising a plurality of logic circuits each comprising switch means (40,57) open and closed in the respective absence and presence of a data input signal, and unidirectional conducting means for blocking transmission of binary signals of said second level and permitting transmission of binary signals of said first level from a said first to a said second line, whereby a first level binary signal is transmitted from each of said first lines in turn to output terminals of said second set selected by said data input signals during said data input time interval.