| 摘要 |
<p>A keyboard coding apparatus, said keyboard having a plurality of keys arranged according to a matrix of c columns and R rows, comprises a scanning interface including a counter (23), a decoder (13) and a multiplexer (22).</p><p>The scanning interface, in consequence of 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.</p><p>Whenever microprocessor 1 sends a pulse to the scanning interface, it increments by one the content of an internal register of its own and, before sending another pulse, processes the signal coming from the scanning interface.</p><p>If the logic level of such signal indicates a condition o' actuated key, the microprocessor draws the character code related to the actuated key from a memory position whose address is latched into its internal register.</p><p>Such keyboard coding apparatus, besides simplifying the keyboard interface unit, considerably reduces the number of connection leads between the microprocessor and the interface unit.</p> |
