The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 01, 2000
Filed:
Oct. 31, 1997
Herman Chang, Hsin-chu, TW;
Yueh-Mei Hou, Tao-Yuan, TW;
Holtek Semiconductor Inc., , TW;
Abstract
A method and an interface circuit for scanning keys and external resistors of a keypad are disclosed. The interface circuit includes: (a) an I/O device including m output ports and n input ports for allowing a key to be set between every two ports of the I/O device to construct a key disposition and allowing external resistors to be set between each of the output ports and each of the input ports to construct an external resistor disposition; (b) a clock generator providing a clock for the I/O device for having each external resistor in the external resistor disposition and each key in the key disposition scanned in response to the clock; (c) an external resistor detector latching a first scanning result of the each external resistor and outputting a first detecting signal in response to the first scanning result for changing a preset function of a system; and (d) a key input detector latching a second scanning result of each key and outputting a second detecting signal in response to the second scanning result to identify a key of the keypad.