KEYBOARD SCANNER

摘要

A keyboard comprises an array of first lines (11) and second lines (12) which are electrically connectable by operation of a key on the keyboard. A first line driver (20) is coupled to each first line (11). A first resistor (31) is connected between each second line (12) and a supply line. Control logic selectively causes the apparatus to operate in: (i) a first state to detect when a key has been pressed; (ii) a second state to perform a keyboard scanning operation to determine which key has been pressed; and (iii) a third state during periods between keyboard scanning operations. Current flow through the first resistors (31) is minimised during the third state.