Patent ID: 6031510
Filing Date: 2000-02-29
Classification: G09G

Abstract:
A method of controlling the updating of a random access memory (RAM) that stores data for coding the activation of pixels of one or more alphanumeric characters of a liquid crystal display (LCD), to maintain substantially an average direct current (DC) voltage value of zero across transparent conductive plates of the LCD, comprising the steps of:employing a type B waveform for activating the LCD, wherein the type B waveform is a waveform which transmits all activation data in two-frame portions, wherein the activation data is assembled in a first frame of each portion and the activation data is assembled in inverse form in a second frame of each portion, whereby an average DC voltage of zero is maintained for the tone B waveform over each of the two-frame portions;allowing the RAM to be written to for updating the data therein only after completion of the second frame of a two-frame portion and before commencement of a new two-frame portion of the type B waveform, to avoid a non-zero value of the average DC voltage over the two-frame portion; anddisallowing an attempt to write to the RAM at times other than between the end of the second frame of a two-frame portion and the commencement of a new two-frame portion of the type B waveform, and setting an error bit as notice of the disallowed attempt.