Holtek Microelectronics Inc.

Holtek Semiconductor Corp.

Utek Semiconductor Corporation

Herman Chang

Yueh-Mei Hou

Ning Chung-Ho

A programmable precise frequency divider cooperating with a low frequency crystal and an oscillating circuit is disclosed. The divider includes a low frequency oscillating circuit, a preset code memory, a programmable preset code loader, an adder, and a register. The programmable preset code loader loads and latches a preset code either from the preset code memory or a preset code input line coupled to an external data source. The latched preset code and the current value of the register are commonly supplied to the adder. The adder is used to sum up the latched preset code from the programmable preset code loader and the current value from the register and thereby supply a resultant value to the register. The register accumulates the resultant value from the adder to the oscillating signal from the oscillating circuit and then supplies a output clock signal with a required divided frequency.

Programmable precise frequency divider

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.

Method and interface circuit for scanning keys and external resistors in

A method and apparatus for improved scanning keyboard and diodes option is disclosed. Each of the pins is treated as one independent dimension so as to define a multi-dimensional configuration. The circuit includes a clock generation circuit, a keyboard I/O port device comprising a plurality of ports associated with the pins and a key detection register device. A key is arranged at the interconnection of any two ports. When the key is depressed, by maintaining the ports at a first level and applying a second level to each of the ports to check which port goes from the first level to the second level, the location of the key may be determined. The output of the ports are stored in the key detection register device for the determination of the key location.

Method and apparatus for scanning keyboard and diode option

A voice-dialing device without additional power supply can generate articulate voice signal upon dialing; such device can provide a function of voice dialing, and a function of confirming the dialing. In dialing operation, the device can provide a correct dialing by using the voice dialing as an auxiliary means; after dialing, a user can confirm the number dialed so as to ensure a user to control the dialing operation and the correctness of a number dialed.

Voice-generating telephone set without external power supply

A compound type keyboard detector is disclosed. It comprises a time-sequencing generator, a keyboard scanner, a column input port and a row input port, a column lock and a row lock, a keyboard-synchronization detector, a keyboard detector and a keyboard decoder. With the unique design of the keyboard detector in conjunction with the various circuits that are associated therewith, a given number of pins can be used for a relatively greater number of input keys, or a smaller number of pins can be used for relatively complicated input keyw. This type of keyboard detector is good for small IC products, and can reduce the manufacturing cost thereof.

Compound type of keyboard detector

A digital-to-analog converter includes a generator responsive to a digital input signal, a set of switches each being directly connected to the generator, and a first and a second terminals connecting therebetween a resistor device having a plurality of nodes directly connected to the switches in order that a node voltage can be obtained between one of the nodes and one of the terminals to serve as an analog signal. Such converter has a low distortion/noise and can be used in a broad source voltage scope.

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Hsinchu, Taiwan

Herman Chang