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:
Jan. 23, 1996
Filed:
Oct. 05, 1994
Keith E Kinerk, Austin, TX (US);
Hoang K Quan, Austin, TX (US);
Joseph P Magliocco, Austin, TX (US);
Motorola, Inc., Schumburg, IL (US);
Abstract
A data processor (50) includes a hardware keyscan circuit (54) to interface to an external keypad matrix (80). In one embodiment, the data processor (50) has a first register (62) for driving data to rows of the keypad matrix (80), and a second register (63) for inputting signals from columns of the keypad matrix (80). A set of weak pullup elements (71) connected to the columns is always conductive. A set of strong pullup elements (75) connected to the columns is conductive only after the hardware keyscan circuit (54) detects that a key (89) is depressed and disables the driving of the rows. Thus, pullup time and power consumption are minimized. The hardware keyscan circuit (54) also includes a data direction register (61) which has a shift control input terminal so that in response to a local state machine (64), the data direction register (61) acts as a shift register to sense the row with the depressed key (89), without intervention from a central processing unit (51).