LCD Controller Pins
11-17
LCD Controller
11.7 LCD Controller Pins
When the shifter is filled, the value is driven to the LCD controller data bus pins
in one of several configurations: LCD.P[3:0] for passive monochrome panels,
LCD.P[7:0] for passive color panels, and LCD.P[15:0] for active displays. In
addition, the pixel clock pin (LCD.PCLK) is toggled. The remaining unused
LCD pixel bits always remain low.
When an entire line of pixels has been output to the LCD screen, the line clock
pin (LCD.HS) is toggled. In the same manner, if the controller is in passive
mode and the start of the first line of a new frame of pixels has been output to
the LCD controller screen, the frame clock pin (LCD.VS) is toggled. To prevent
a dc charge from building within the screen pixels, the display power and
ground supplies are periodically switched. The LCD controller signals the dis-
play to switch the polarity by toggling the ac-bias pin (LCD.AC). The user can
control the frequency of the bias pin by programming the number of line clock
transitions between each toggle.
When active display mode is enabled, the timing of the pixel, line, and frame
clocks and the ac-bias pin change. The pixel clock transitions continuously in
this mode for as long as the LCD is enabled. The ac-bias pin functions as an
output enable. When it is asserted, the display can use it to latch data from the
LCD pins using the pixel clock.
The timing of the line and frame clock pins is programmable to support both
passive and active mode. Programming options include:
-
Delay insertion both at the beginning and end of each line and frame (front
and back porch)
-
Pixel clock, line clock, frame clock, and ac-bias signal polarity
-
Line and frame clock pulse width
If the LCD is disabled, the signals LCD.P[15:0] are set to 0 and LCD.PCLK,
LCD.VS, LCD.HS, and LCD.AC are set to their inactive state. This can be 0
or 1 depending on the inversions programmed in the timing 2 register. See
Table 11–24.
The OMAP5910 LCD controller provides outputs compatible with passive
monochrome, passive color (STN), and active color (TFT) displays. Recom-
mended connections to each type of display are outlined in the sections below.