Communications: electrical – Audible indication – Percussion-type sound producer
Patent
1982-04-30
1985-02-26
Groody, James J.
Communications: electrical
Audible indication
Percussion-type sound producer
340365E, G06F 302
Patent
active
045020396
ABSTRACT:
Keyboard coding apparatus couples to a plurality of keys and comprises a scanning interface including a counter (23), a decoder (13) and a multiplexer (22). The scanning interface, in response to each pulse received from a microprocessor (1) through an input lead (11), sends to the microprocessor on an output lead (10) a logic signal indicative of the state of any selected one of the keys. Whenever microprocessor 1 sends a pulse to the scanning interface, it increments by one the contents of an internal register and, before sending another pulse, processes the signal from the scanning interface. When the logic level of such signal indicates a condition of an actuated key, the microprocessor waits a predetermined time interval to establish that said selected key activation is valid, then waits until the selected key has been deactivated and then accesses the character code related to the actuated key from a memory location whose address is latched into its internal register. Besides simplifying the keyboard interface unit, such keyboard coding apparatus reduces considerably the number of connection leads between the microprocessor and the interface unit.
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Marzocca Francesco
Vercesi Arturo
Driscoll Faith F.
Groody James J.
Honeywell Information Systems Italia
Prasinos Nicholas
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