🚀 go-pugleaf

In sci.electronics, tidedu@mars.lerc.nasa.gov (William T. Dedula) writes:
>Hello All;
>I am building a project which requires a LCD counter. I am using
>MM74HC4543's to drive each of the 4 digit's BUT I need to drive
>a few special indicators on the LCD panel such as a LOW BATT
>indicator. I'd like to know how I can do this ? Would the normal
>proceedure be to use another MM74HC4543 or is there a simpler way ?
>
    Use an XOR gate (74HC86, etc.).  Connect one XOR input to the signal
you want to indicate ("Low Batt" comparator output); drive the other
input with the LCD backplane clock signal; connect the XOR output to
the LCD segment ("LOW BATT").  When the first XOR input is low, the
output is in phase with the backplane clock and the segment is blank;
when high, the XOR inverts, the output is out of phase and the segment
is visible.

-DaveP