Functional Description
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13.3.2 LCD External I/O Signals
Table 13-4 shows the details of the LCD controller external signals.
Table 13-4. LCD External I/O Signals
Signal Type Description
LCD_VSYNC OUT Raster controller: Frame clock the LCD uses to signal the start of a new frame of pixels.
Also used by TFT displays as the vertical synchronization signal.
LIDD character: Register select (RS) or address latch enable (ALE)
LIDD graphics: Address bit 0 (A0) or command/data select (C/D)
LCD_HSYNC OUT Raster controller: Line clock the LCD uses to signal the end of a line of pixels that transfers
line data from the shift register to the screen and to increment the line pointer(s). Also used
by TFT displays as the horizontal synchronization signal.
LIDD character: not used.
LIDD graphics:
• 6800 mode = read or write enable
• 8080 mode = not write strobe
LCD_PCLK OUT Raster controller: Pixel clock the LCD uses to clock the pixel data into the line shift register.
In passive mode, the pixel clock transitions only when valid data is available on the data
lines. In active mode, the pixel clock transitions continuously, and the ac-bias pin is used
as an output enable to signal when data is available on the LCD pin.
LIDD character: not used.
LIDD graphics:
• 6800 mode = enable strobe
• 8080 mode = not read strobe
LCD_AC_BIAS_EN OUT Raster controller: ac-bias used to signal the LCD to switch the polarity of the power
supplies to the row and column axis of the screen to counteract DC offset. Used in TFT
mode as the output enable to signal when data is latched from the data pins using the pixel
clock.
LIDD character: Primary enable strobe
LIDD graphics: Chip select 0 (CS0)
LCD_MCLK OUT Raster controller: not used.
LIDD character: Secondary enable strobe
LIDD graphics: Chip select 1 (CS1)
LCD_D[23:0] Raster: OUT LCD data bus, providing a 4-, 8-, 16- or 24-bit data path.
Raster controller: For monochrome displays, each signal represents a pixel; for passive
color displays, groupings of three signals represent one pixel (red, green, and blue).
LCD_DATA[3:0] is used for monochrome displays of 2, 4, and 8 BPP; LCD_DATA[7:0] is
used for color STN displays and LCD_DATA[15:0] or LCD_DATA[23:0] is used for active
(TFT) mode.
LIDD: OUT/IN LIDD character: LCD_DATA[15:0] Read and write the command and data registers.
LIDD graphics: LCD_DATA[15:0] Read and write the command and data registers.
1104
LCD Controller SPRUH73H–October 2011–Revised April 2013
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