Patent ID: 6020833
Filing Date: 2000-02-01
Classification: H03M

Abstract:
An interface circuit adapted to be connected to a keypad comprising:an I/O device having a plurality of keys, a plurality of external resistors, a first number m of output ports and a second number n of input ports for allowing keys to be set between every two ports of said I/O device to construct a key disposition and allowing each of said plurality of external resistors to be set between each of said output ports and each of said input ports to construct an external resistor disposition, wherein m and n are natural numbers;a clock generator electrically connected to said I/O device and providing a clock for said I/O device for scanning each external resistor in said external resistor disposition and each key in said key disposition in response to said clock;an external resistor detector electrically connected to said I/O device and said clock generator for latching a first result of scanning said each external resistor and outputting a first detecting signal in response to said first result; anda key input detector electrically connected to said I/O device and said clock generator for latching a second result of scanning said each key and outputting a second detecting signal in response to said second result such that a pressed key of said keypad is identified according to said first and second detecting signals.