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LCD Controller
8-6
MC68328 USER’S MANUAL 12/9/97
MOTOROLA
LCD
CONTROLLER
8
PRELIMINARY
8.2.2 Interfacing the LCD Controller with an LCD Panel
With the following signals, you can interface the LCD controller to an LCD panel.
8.2.2.1 LCD DATA BUS SIGNALS. The LD3–LD0 signals output bus transfers pixel data
to the LCD panel for display. Data is arranged differently on the bus depending on the LCD
data-width mode selected, as shown in Figure 8-3. System software can also program the
output pixel data to be inverted. See Section 8.6.2 LCD Polarity Configuration Register
for more information.
The LCD data bus uses LD0 to display pixel 0, 0. Some LCD panel manufacturers specify
their LCD panel data bus in which data bit 3 of the panel displays pixel 0,0. For these panels,
connections from the DragonBall’s LD bus to the LCD panel data bus are reversed in bit
significance (LD3 connects to panel data 0, LD2 to panel data 1, LD1 to panel data 2, and
LD0 to panel data 3).
8.2.2.2 LCD FIRST LINE MARKER SIGNAL. The LFLM signal indicates the start of a new
display frame. It becomes active after the first line pulse of the frame and remains active until
the next line pulse, at which point it deasserts and remains inactive until the next frame. You
can program the LFLM signal to be active-high or active-low. See Section 8.6.2 LCD
Polarity Configuration Register for details.
8.2.2.3 LINE PULSE SIGNAL. The LP signal latches a line of shifted data into the LCD
panel. It becomes active when a line of pixel data is clocked into the LCD panel and stays
asserted for a duration of eight pixel clock periods. You can program the LP signal to be
either active-high or active-low. See Section 8.6.2 LCD Polarity Configuration Register
for details.
8.2.2.4 LCD SHIFT CLOCK SIGNAL. The LSCLK signal is the clock output that is
synchronized to the LCD panel output data. Your system software can program the LSCLK
signal to be either active-high or active-low. See Section 8.6.2 LCD Polarity Configuration
Register for details.
8.2.2.5 LCD ALTERNATE CRYSTAL DIRECTION SIGNAL. The LACD output signal is
toggled to alternate the crystal polarization of the panel. This provides an AC polarity change
that prevents crystal degradation of the LCD panel caused by DC voltage. Your system
software can program this signal to toggle at a 1 to 16 frame period. The alternate crystal
direction (LACD or M) pin will toggle after the preprogrammed number of FLM pulses. Your
system software can also program the ACD rate control register (LACDRC) so that LACD
will toggle once every 1–16 frames. The targeted number of frames is equal to the alternate
code’s 4-bit value plus one. The default value for LACDRC is zero, which means LACD will