26 LCD CONTROLLER (LCDC)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
26-29
Display Control
26.6
Controlling LCD Power Up/Down
26.6.1
The LCD controller is activated when the LCDC clocks are supplied from the CMU. Following initial reset, the
LCD controller is set in power-save mode. Supplying the clocks does not immediately cause the LCD panel to ini-
tiate a power-up sequence and start displaying data. When the LCD panel is placed in power-save mode, all LCD
signal output pins are fixed at low.
To change the LCD controller from power-save mode back into normal mode, set the PSAVE[1:0]/LCDC_PSAVE
register to 0x3. The LCD controller starts a power-up sequence from that point, and outputs LCD signals. Con-
versely, to change from normal mode to power-save mode, set PSAVE[1:0] to 0x0. The LCD controller starts a
power-down sequence from that point, and drives the LCD signals low.
The LCD control registers and look-up tables can be accessed even in power-save mode.
If the power to the LCD panel is turned on or off while LCD signals are not being correctly output, the panel may
be damaged. Therefore, the power to the LCD panel must be turned on only after the LCD controller starts control-
ling LCD signals. Use an I/O port to control the power to the LCD panel for this purpose. When LCD signals have
no effect, disable the LCD power supply by controlling the port output; when LCD signals become effective, enable
the LCD power supply using the port.
The procedure for initializing the LCD at power-on is summarized below.
1. Configure the clocks, pins, and display memory area (refer to “26.4 System Settings”).
2. Set the LCD-panel parameters, display mode, and look-up tables (refer to “26.5 Setting the LCD Panel”).
3. Enable the LCDC interrupt.
4. Write display data to the display memory.
5. Set the display start address (refer to “26.6.2 Main Window Display Start Address and Virtual Screen Set-
tings”).
6. Place the LCD controller in normal mode (PSAVE = 0x3).
7. The LCD controller starts outputting the LCD signals.
8. Wait time should be inserted depending on the LCD panel power source.
9. Control the port to turn the LCD panel power on.
The following is the power-down procedure.
1. Control the port to turn the LCD panel power off.
2. Wait time should be inserted depending on the LCD panel power source.
3. Place the LCD controller in power-save mode (PSAVE = 0x0).
4. The LCD controller pulls LCD signals down to low.
Main Window Display Start Address and Virtual Screen Settings
26.6.2
Main window display start address
The display memory address from which to start display for the main window can be changed as desired us-
ing the LCDC_MAINADR register. The start address set in this register corresponds to the upper left edge of
the LCD panel. Note that a word boundary address (A[1:0] = 0b00) in IVRAM or the external VRAM must be
specified to this register.
Main screen address offset for virtual screen
The S1C33L26 LCDC supports a virtual screen feature to use the VRAM with a different size from that of the
LCD panel.