hd66789 Renesas Electronics Corporation., hd66789 Datasheet - Page 59

• Manufacturer Part Number: hd66789
• Description: 528-channel, One-chip Driver For Amorphous Tft Panels With 262,144-color Display Ram, Power Supply Circuit, And Gate Circuit
• Manufacturer: Renesas Electronics Corporation.

HD66789
RAM Access through RGB-I/F and System I/F
The HD66789 writes all display data on the screens to the internal RAM. This enables the transfer of only
the data for the moving picture area as well as for the frames for updating screens through the RGB
interface. By writing data in the high speed write mode (HWM = 1) and with the window address function,
the HD66789 enables a high-speed access to RAM with low power consumption while displaying moving
pictures. In the frames other than the moving picture screen update, the display data in the area other than
the moving picture area can be updated through a system interface.
The RAM access is also possible through a system interface even in the RGB-I/F mode. In the RGB
interface mode, data are written to RAM in synchronization with the DOTCLK during ENABLE = “Low”.
When writing data in the RGB-I/F mode through the system interface, it is necessary to set the ENABLE
“High” to stop writing through the RGB interface. After accessing to RAM through the system interface,
wait an enough time for the write/read bus cycle before starting accessing to RAM through the RGB
interface. When RAM accesses through the RGB and system interfaces conflict, there will be no guarantee
that data are properly written to RAM.
Rev.0.12, May 09 2003, page 59 of 156
System interface
VSYNC
ENABLE
DOTCLK
PD17-0
Updating Still Picture Area during Displaying a Moving Picture
Setting of index
Index
R22
Updating
(both panels)
Updating or moving
picture area
Note 1) When RGB-I/F is selected, the address setting is made at every falling edge of VSYNC.
Note 2) The address set and the index set must be made before the RAM access throught the RGB interface.
Note 3) The high-speed write mode should be used in RGB-I/F and VSYNC-I/F modes.
RM=0
address
Setting
of
Index
R22
Updating still picture area*1
2001/01/01 00:00
other than moving
Updating of area
Moving picture area
picture area
Still picture area
RM=1
address
Setting
of
Index
R22
Updating or moving
Updating
(both panels)
picture area
Preliminary