US4598174A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Circuit for detecting keypad conditions in a microprocessor controlled telephone instrument
Assignee: AG Communication Systems Corp
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Filing: 1984-11-13
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Granted: 1986-07-01
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Expires: 2004-11-13
Abstract
Abstract A technique for evaluating keypad conditions while utilizing only a minimum number of ports in a microprocessor involved in control of a telephone instrument. Because of the limited number of ports available and necessity to also evaluate conditions of mode selecting strap switches, the utilization of a reduced number of ports is highly desirable in such an enviroment. Such a reduction becomes an absolute necessity particularly in dealing in those enviroments that include random access memories, read only memories, pulse dialers, integrated circuits and liquid crystal displays. A combination of diode gating, resistive decoupling and time multiplexing techniques are used to match the input/output requirements to the available ports of a specific microprocessor.
Inventors
- 👤 II Karl E. Pommer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 15:07
CPC Classifications
H; H04; H04M; H04M1/00; H04M1/26
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
139 words
A circuit arrangement adapted to maximize the utilization of a microprocessor associated with a telephone comprising: a microprocessor including a plurality of four pin ports and a serial output port; the pins of a first port connected as an output to the circuitry of an associated telephone; said serial output port connected to a shift register; said shift register further including a plurality of parallel circuit outputs connected to a random access memory; the pins of a second port connected as inputs to said random access memory; the pins of a third port also each connected to data in-out connections of said random access memory and each pin of said third port also connected to a DTMF dialer circuit; and one of said pins of said first port also connected to an enable input of said DTMF dialer circuit.
Claim 2
Dependent Claim
139 words
A circuit arrangement adapted to maximize the utilization of a microprocessor associated with a telephone comprising: a microprocessor including a plurality of four pin ports and a serial output port; the pins of a first port connected as an output to the circuitry of an associated telephone; said serial output port connected to a shift register; said shift register further including a plurality of parallel circuit outputs connected to a random access memory; the pins of a second port connected as inputs to said random access memory; the pins of a third port also each connected to data in-out connections of said random access memory and each pin of said third port also connected to a DTMF dialer circuit; and one of said pins of said first port also connected to an enable input of said DTMF dialer circuit.
Claim 3
Dependent Claim
31 words
A circuit arrangement as claimed in claim 1 wherein: there is further included a liquid crystal display and a plurality of circuit connections between said liquid crystal display and said microprocessor.
Claim 4
Dependent Claim
83 words
A circuit arrangement as claimed in claim 1 wherein: there is further included a keypad associated with said telephone including a plurality of column output lines connected to the pins of a fourth port; said keypad further including a plurality of parallel row output conductors connected to a multiplexer; said multiplexer including a plurality of outputs connected to the pins of a fifth port; and a pair of select outputs from said multiplexer connected to two of the pins of said second port;
Claim 5
Dependent Claim
55 words
A circuit arrangement as claimed in claim 3 wherein: there is further included an output from at least one strap switch connected to at least one of the pins of said fourth port and a circuit conductor from at least one of said strap switches connected to one of said pins of said second port.
Claim 6
Dependent Claim
22 words
A circuit arrangement as claimed in claim 4 wherein: said telephone further includes a hookswitch including circuit connections to said fourth port.
Claim 7
Dependent Claim
30 words
A circuit arrangement as claimed in claim 4 wherein: there is further included an inverter circuit included in each column output line connected to the pins of said fourth port.
Claim 8
Dependent Claim
27 words
A circuit arrangement as claimed in claim 6 wherein: each of said column output lines further include a diode serially connected between said inverter and said keypad.
Claim 9
Dependent Claim
37 words
A circuit arrangement as claimed in claim 4 wherein: the output voltage from said strap switch is decoupled by a resistor element to inhibit any effect on output data from said microprocessor to said keypad control lines.
References Cited (Backward Citations)
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US4513175A
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US4475013A
Cited
US4503291A
Cited
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Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-06-30 | 1989-12-30 | 1990-07-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-06-30 | 1993-12-30 | 1994-07-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-06-30 | 1997-12-30 | 1998-07-01 | $7700.00 | Window Closed / Lapsed |