HD66787 Datasheet, PDF (20/159 Pages) Renesas Technology Corp – 528-channel, One-chip Driver with 262,144-color Display RAM and Power Supply Circuit for Low-temperature Poli-Si TFT (LTPS-TFT) Panels with Incorporat

HD66787
Preliminary
2. External Display Interface
The HD66787 incorporates RGB and VSYNC interfaces as an external interface for displaying moving
pictures. When RGB-I/F is selected, the display operation is executed in synchronization with the
externally supplied signals, VSYNC, HSYNC, and DOTCLK. The display data (PD17-0) are written
according to the values of data enable signal (ENABLE) and data valid signal (VLD) in synchronization
with VSYNC, HSYNC, and DOTCLK signals. This data write method allows flicker-free screen update.
When VSYNC-I/F is selected, operations other than the frame synchronization by VSYNC signal are
synchronized with internal clocks. The display data are written to GRAM through a system interface. In
this case, there are constraints on the timing and methods of RAM update. See the “External Display
Interface” section for more details.
Switching between conventional system interfaces and external display interfaces is made through
instructions. An optimum interface is selected whether the screen is displaying moving or still pictures.
All data written through RGB-I/F are written to GRAM. Therefore, data is transmitted only when the
screen is being updated, which reduces the amount of data transmission, thereby saving power when
moving pictures are being displayed.
3. Bit Operations
The HD66787 supports a write data mask function that selects and writes data into GRAM by bit, and
performs logical operation or conditional rewrite on the contents of compare registers and the data to write
to GRAM. For details, see the “Graphics Operation Functions” section.
4. Address Counter (AC)
Address counter (AC) assigns address to GRAM. When an address set instruction is written into the IR, the
address information is sent from the IR to the AC.
After writing data to GRAM, the AC is automatically updated plus or minus 1. The AC is not updated
when the data are read from GRAM. Window address function enables data write only in the rectangular
area of GRAM specified by the window address.
5. Graphics RAM (GRAM)
GRAM is a graphics RAM that stores bit-pattern data of 176 x 240 bytes with 18 bits per pixel.
6. Grayscale Power Supply Voltage Generating Circuit
Grayscale voltage generation circuit generates liquid crystal drive voltage according to the grayscale data
set in the γ-correction register, enabling 262,144-color display. For details, see the “γ-Correction Register”
section.
7. Timing Generator
Timing generator generates timing signals for the operation of internal circuits such as GRAM. The timing
for display operation such as RAM read and the internal operation timing such as access from MPU are
generated in a way to avoid mutual interfere. The interface signals (M, FLM, CL1, EQ, DCCLK,
Rev.0.22, May.23.2003, page 20 of 159