LCD Data processor driver and method

Details LCD Data processor driver and method LCD Data processor driver and method

1978-08-10

1981-06-02

Trafton, David L.

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

340802, 340811, 350332, G08B 536

Patent

active

042714109

ABSTRACT:
The invention is a method and apparatus for multiplexing liquid crystal displays of increased numbers of alphanumeric characters without shadowing or flicker and minimizes contrast degradation. Bipolar segment voltages are interrelated to bipolar tri-level backplane voltages for logical selection of voltage differences across the segments to provide either energization or less than threshold voltage application. The polarities of the bipolar voltages are automatically reversed at the end of each cycle of sequential application of backplane voltages to all backplanes to avoid metallization plating problems in the display. Power level shift is accomplished in the logic stage for the display, and CMOS active gate elements are used in lieu of power consuming resistive networks for a total power requirement of less than 5 milliwatts to multiplex and drive up to 7 characters of 16 segments each. Simplified interfacing with a microprocessor is provided using standard 8 bit bus and control signals. A FIFO is loaded by the processor and the segment data signals are applied to the LCD at a relatively slow rate which releases the processor for other duties most of the time. An op amp voltage supply produces the bipolar segment voltages equally and oppositely spaced from a reference backplane voltage. It also provides for adjustment of the segment voltages while maintaining the equal and opposite relation to accommodate different threshold values of multiplexing fluids.

REFERENCES:
patent: 3694662 (1972-09-01), Grygera et al.
patent: 3896430 (1975-07-01), Hatsukano
patent: 3898646 (1975-08-01), Washizuka et al.
patent: 3911426 (1975-10-01), Mouton et al.
patent: 3976994 (1976-08-01), Washizuka et al.
patent: 4038564 (1977-07-01), Hakata
patent: 4060801 (1977-11-01), Stein et al.
patent: 4062626 (1977-12-01), Kawakami et al.
patent: 4121203 (1978-10-01), Edwards et al.

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