Liquid crystal display controller and liquid crystal display device
In conventional liquid crystal display controllers such as for portable telephone sets, the display is reduced in the stand-by state but the liquid crystal display duty is not changed, i.e., even the common electrodes of the rows that are not producing display are scanned, and the consumption of electric power is not decreased to a sufficient degree in the stand-by state. A liquid crystal display controller ( 2 ) includes a drive duty selection register ( 34 ) capable of being rewritten by a microprocessor ( 1 ), and a drive bias selection register ( 32 ). When the display is changed from the whole display on a liquid crystal display panel ( 3 ) to a partial display on part of the rows only, the preset values of the drive duty selection register and of the drive bias selection register are changed, so that the display is selectively produced on a portion of the liquid crystal display panel at a low voltage with a low-duty drive.
1. A portable telephone comprising:
a liquid display panel having a plurality of first electrodes provided in a first direction and a plurality of second electrodes provided in a second direction which crosses in the first direction; and
a liquid crystal display controller mounted on glass substrate that constitute the liquid display panel, coupled to the liquid display panel and for driving a liquid display panel, the liquid crystal display controller being enable to setting up a partial display area on the display panel by controlling a driving of ones of the plurality of second electrodes, the liquid crystal display controller comprising:
an interface circuit coupled to receive signals provided from an outside of the liquid crystal display controller;
a display RAM coupled to the interface circuit and storing display data to be displayed on the liquid display panel;
an address counter providing addresses of the display RAM;
a timing generation circuit;
a first driver coupled to the timing generation circuit and providing signals for driving the plurality of the first electrodes;
a second driver providing signals for driving the plurality of second electrodes in accordance with the display data read out from the display RAM; and
a display position setting register coupled to the interface circuit and designating a position of the partial display area on the display panel,
wherein the display position setting register is capable of being rewritten from the outside of the liquid crystal display controller via the interface circuit,
wherein the first driver provides signals for driving ones of the plurality of first electrodes which are designated by the display position setting register, and the first driver provides a voltage of non-selection level to the other of the plurality of first electrodes which correspond to non-display area other than the partial display area in the liquid display panel.
2. A portable telephone according to claim 1 , wherein the liquid crystal display controller further comprises:
a boosting circuit providing voltages to the first and the second driver; and
a boost power setting register coupled to the interface circuit and setting a boost power of the boosting circuit.
3. A portable telephone according to claim 2 ,
wherein the boost power setting register is capable of being rewritten from the outside of the liquid crystal display controller via the interface circuit.
4. A portable telephone according to claim 2 ,
wherein the boosting circuit has a terminal to be coupled to a capacitance which is to be provided at the outside of the liquid crystal display controller.
5. A portable telephone according to claim 3 ,
wherein the boosting circuit is capable of boosting up a voltage supplied from the outside of the liquid crystal display controller in twice or three times.
6. A portable telephone according to claim 1 ,
wherein the first driver does not provide a voltage of non-selection level in an AC drive to the other of the plurality of first electrodes which correspond to non-display area other than the partial display area in the liquid display panel.