Data processor with a hardware keyscan circuit, hardware keyscan

Details Data processor with a hardware keyscan circuit, hardware keyscan Data processor with a hardware keyscan circuit, hardware keyscan

1994-10-05

1996-01-23

Peng, John K.

Coded data generation or conversion

Bodily actuated code generator

Including keyboard or keypad

341 24, 341 25, 364189, 34082577, H03K 1794

Patent

active

054868246

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).

REFERENCES:
patent: 4305065 (1981-12-01), Mogi
patent: 4348670 (1982-09-01), DeShon
patent: 4408191 (1983-10-01), Fowler
patent: 4409665 (1983-10-01), Tubbs
patent: 4922248 (1990-05-01), Shiga
patent: 5101201 (1992-03-01), Choi
patent: 5254989 (1993-10-01), Verrier et al.
patent: 5264845 (1993-11-01), Kwon et al.
patent: 5280283 (1994-01-01), Raasch et al.
patent: 5384721 (1995-01-01), Joto
MC68HCO5PG&E Specification Revision 1.0, Section 4.1.3 Keyboard Scanner, pp. 31-33.
MC68HC05HG Release 1.4, Section 5 Input/Output Ports, pp. 37-47.

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