Intel PXA250 and PXA210 manual LCD Display Controller, LCD Display Overview, Passive DSTN Displays

LCD Display Controller 3

This chapter describes sample hardware connections from the PXA250 applications processor to various types of LCD controllers. Active (TFT) as well as passive (DSTN) displays are discussed as well as single and dual panel displays. These should not be considered the only possible ways to connect an LCD panel to the PXA250 applications processor, but should serve as a reference to assist with hardware design considerations. Other panels, for example panels without L_FCLK or L_LCLK, have been successfully connected to the PXA250.

3.1LCD Display Overview

The PXA250 applications processor supports both active and passive LCD displays. Active displays generally produce better looking images, but at a higher cost. Passive displays are generally less expensive, but their displays are inferior to active displays. However, recent advances in dithering technology are closing the quality gap between passive and active displays.

Note: Names used for “LCD Panel Pin” are representative names and may not match those on all LCD panels. Refer to the LCD panel reference documentation for the actual name.

3.2Passive (DSTN) Displays

Several different types of passive displays are available in both color and monochrome. These maybe single or dual panel displays. Additionally, some monochrome displays use double-pixel data mode (twice the number of pixels as a normal monochrome display). With the exception of the number of data pins required, all of these choices affect the software configuration and support, not the system hardware design. In fact, most passive displays use a single interconnection scheme. For information on the software changes and performance considerations of the various display options, refer to the PXA250 and PXA210 Applications Processors Developer’s Manual.

Passive displays drive dithered data to the LCD panel - which means that for each pixel clock cycle a single data line drives an ON/OFF signal for one color of a single pixel.

Table 3-1describes the number of L_DD pins required for the various types of passive displays, as well as which LCD data pins are used for which panel (upper or lower).

Table 3-1. LCD Controller Data Pin Utilization (Sheet 1 of 2)

Color/	Single/	Double-Pixel
Monochrome			Screen Portion	Pins
	Dual Panel	Mode
Panel
Monochrome	Single	No	Whole	L_DD<3:0>
Monochrome	Single	Yes	Whole	L_DD<7:0>1
Monochrome	Dual	No	Top	L_DD<3:0>
			Bottom	L_DD<7:4>
Color	Single	N/A	Whole	L_DD<7:0>

PXA250 and PXA210 Applications Processor Design Guide 3-1