Browse Prior Art Database

AREA EFFICIENT, LOW POWER LCD CONTROLLER WITH EXTERNAL BITMAPPED CURSOR

IP.com Disclosure Number: IPCOM000008451D
Original Publication Date: 1997-Dec-01
Included in the Prior Art Database: 2002-Jun-14
Document File: 4 page(s) / 179K

Publishing Venue

Motorola

Related People

Irfan Furniturewala: AUTHOR [+2]

Abstract

Liquid Crystal Display (LCD) controllers in pager applications typically have simple cursor display such as a block shape with blink capability. Display of complex graphic cursor is typically done in software which requires a lot of power and time. As such, traditional pagers cursor display have limited shapes and features in order to save power. This article describes a method in which complex cursor shapes can be displayed using hardware with minimal area cost and power consumption Traditionally, Liquid Crystal Display (LCD) Controllers display complex graphic cursors via software; since the available hardware cursor on them is very simple. Software implementation is obviously expensive, in terms of power and time, since every time the cursor is moved, the entire external screen display memory has to be updated. The low power LCD Controller implements a bitmapped cursor in hardware, thus reducing the power consumption and software time overhead. At the same time the effective area-increase is mini- mized by storing the cursor bitmap in external memory instead of having internal registers and utilizing the Direct Memory Access (DMA) sub- module already existing on the LCD controller. The DMA transfers cursor data from external memory to an internal register only when cursor data is required, as determined by the internal logic thus minimizing power and area. The Low Power LCD Controller is thus an excellent candidate for modem graphic-oriented, low-power, area-efftcient micro- controllers.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 38% of the total text.

Page 1 of 4

m MOTOROLA Technical Developments

AREA EFFICIENT, LOW POWER LCD CONTROLLER WITH EXTERNAL BITMAPPED CURSOR

by Han Furniturewala and Yong Kim

ABSTRACT

  Liquid Crystal Display (LCD) controllers in pager applications typically have simple cursor display such as a block shape with blink capability. Display of complex graphic cursor is typically done in software which requires a lot of power and time. As such, traditional pagers cursor display have limited shapes and features in order to save power. This article describes a method in which complex cursor shapes can be displayed using hardware with minimal area cost and power consumption

INTRODUCTION

  Traditionally, Liquid Crystal Display (LCD) Controllers display complex graphic cursors via software; since the available hardware cursor on them is very simple. Software implementation is obviously expensive, in terms of power and time, since every time the cursor is moved, the entire external screen display memory has to be updated. The low power LCD Controller implements a bitmapped cursor in hardware, thus reducing the power consumption and software time overhead. At the same time the effective area-increase is mini- mized by storing the cursor bitmap in external memory instead of having internal registers and utilizing the Direct Memory Access (DMA) sub-

module already existing on the LCD controller. The DMA transfers cursor data from external memory to

an internal register only when cursor data is required, as determined by the internal logic thus minimizing power and area. The Low Power LCD Controller is thus an excellent candidate for modem graphic-oriented, low-power, area-efftcient micro- controllers.

DESCRIPTION

  LCD Controllers(LCDC) provide display data for an external LCD panel. The LCDC frame buffer, typically, resides in external system memory, instead of a dedicated display RAM buffer to reduce system cost. A built-in screen DMA fetches data from the frame buffer and places the data in an internal line buffer. The internal LCDC logic then shifts out the data in the line buffer to an external LCD panel module for screen refresh. Conventional LCD controllers have a simple hardware block cur- sor with features such as programmable dimen- sions, reverse-video, blinking, etc. To implement sophisticated shapes such as hour-glass or an arrow, the LCD controller relies on software. Typically, software treats the bitmapped cursor as part of the display screen, resident in external memory. It needs to re-write the entire screen, every time the cursor is moved. This obviously requires additional overhead in power and timing. Figure 1, "Block Diagram of a Simple Curor LCD Controller," shows a simple LCD Controller with no support for bitmapped cursor.

t, MOfOrol& 1°C. ,997 100 December 1997

[This page contains 14 pictures or other non-text objects]

Page 2 of 4

MO-LA Technical Developments

LCD CONTROLLER

EXTERNALMEMORY !------------------,

r

Pixel Data

-j-~-qjz+

I L---7

LCD SCREEN

I I

I

I...