hd66789 Renesas Electronics Corporation., hd66789 Datasheet - Page 107

• 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
Write-data Mask Function
The HD66789 expands the 16-bit data sent from the microcomputer into the 18-bit data. In the18-bit
interface mode, data are not expanded. The write data mask function of the HD66789 controls the write
operation of the 18-bit data from the microcomputer to GRAM by bit. The write data mask function write
data in the bits whose corresponding bits in the write data mask resister (WM17–0) are assigned with “0”.
It does not write data in the bits whose corresponding bits in the write data mask register (WM17–0) are
assigned with “1”, and the corresponding data in GRAM are not overwritten but retained. This function is
useful when only one-pixel data are rewritten or a particular color in the display is selectively changed.
Graphics Operation Processing
1. Write mode 1: AM = 0, LG2–0 = 000
This mode is used when data are horizontally written in high-speed mode. It is also used to initialize the
graphics RAM (GRAM) or to draw a line horizontally. The write-data mask function (WM17–0) is also
available with this mode. After writing, the address counter (AC) automatically increments by 1 (I/D = 1)
or decrements by 1 (I/D = 0), and jumps to the counter at the opposing edge of the next one-raster-row
below after when the counter reaches either left or right edge of GRAM.
Rev.0.12, May 09 2003, page 107 of 156
Write-data mask:
Operation example
1) I/D = "1", AM = "0", LG2-0 = "000"
2) WM17-0 = "00FFF"H
3) AC = "0000"H
1 0 0
Write-data (2)
Write-data (1)
Write data (1)
the microcomputer
1
Write data mask
1 1
GRAM data
Data from
“0000”H
*
*
DB17
WM17
1 0 0
1 1 0
0 0 0
*
*
WM17
*
DB17
R05 R04 R03 R02 R01 R00 G05 G04 G03 G02 G02 G01 G00 B05 B04 B03 B02 B01 B00
1
0
17
0
* * * * * *
1
* *
Note : Data are expanded into 18 bits in the 8/16-bit system interface and the 16 RGB interface modes.
1 1
0 1
0 0
1
*
1
0
1
* *
1
1
0
1
1
0
1
*
1
Write data mask function
1
0
1
*
0
0
1
1
1 1 0
0 1
1 1
1 1
1
0
0
Write Mode 1
G05
1
0
0
Write data (2)
1 0
0 0
GRAM
1 1
G04 G03 G02 G02 G01 G00
0 1
0
“ 0001” H
WM0
DB0
0
0
1
0
0
*
0
1
*
0
*
*Write-mask <G>, <B> planes.
Data are expanded into 18 bits in 8/16-bit system
interface, and 16-bit RGB interface modes.
*
0
*
* *
0
Note : The bits
*
0
* *
1
* * * *
*
are not overwritten.
1
*
1
in the GRAM with “ " *"
1
B01 B00
“ 0002”H
0
DB0
WM0
0
0
Preliminary