
LCD Controller
18-16
MPC823 USER’S MANUAL
MOTOROLA
LCD
CONTROLLER
18
18.3.9.3 ACTIVE INTERFACE. Active (TFT) interfaces use the following signals. These
signals have a programmable polarity. Tcyc is the cycle time of the LCD clock (SHIFT/CLK).
Figure 18-12, the reference to 1-16 lines signifies that the time period depends on how the
VPW field in the LCVCR is programmed. The reference to 0-1,023 lines signifies that the
time period varies between 0 and 1,023 scan lines (WBF field in the LCVCR).
SHIFT/CLK—When the LCD output enable signal is valid, data is latched on the
asserted edge of CLK.
FRAME/VSYNC—This vertical sync signal initiates a new frame.
LOAD/HSYNC—This horizontal sync signal initiates a new line.
LCD_AC/LOE—When the LCD output enable signal is valid it enables data to be shifted
into the display. When it is disabled, the data is invalid and no data is transferred.
LD—The LCD data bus represents 4-, 8-, or 12-bit data. For monochrome displays, 4-
or 8-bit data is the same as passive interfaces and 12-bit data is used for color displays.
Use the following formulas to calculate the HSYNC and VSYNC cycles using the
user-programmable parameters that are located in the LCD control registers.
VSYNC = (HSYNC
× L) +WBF
HSYNC = SHIFT/CLK
× (P ÷ LCDBW +12 + TWBL)
SHIFT/CLK = LCDCLK
× F
LCDCLK = VCOOUT
× LCD_div_factor (programmed)
Where:
L = Number of lines in panel (
÷2 for dual-scan displays and +VPW in LCVCR for active).
WBF = Number of waits between frames.
P = Number of pixels per line in panel (
×2 for dual-scan displays).
LCDBW = LCD bus width (4- or 8-bit for passive displays and 1 for active).
TWBL = Total number of waits between lines.
VCOOUT = SPLL output frequency.
LCD_div_factor = LCD_div_factor is programmed in the SCCR (DFLCD
× DFALCD).
F = Inner rate factor that depends on your configuration:
3:
For a four bits per pixel color passive display with an 8-bit LCD data bus width
single-scan.
2:
For a four bits per pixel color passive display with an 8-bit LCD data bus width
dual-scan or with a 4-bit LCD data bus width single-scan.
1:
For all other configurations.