hd66765 Renesas Electronics Corporation., hd66765 Datasheet - Page 55

• Manufacturer Part Number: hd66765
• Description: 396-channel Segment Driver With Internal Ram For 4096-color Displays - Hitachi Semiconductor
• Manufacturer: Renesas Electronics Corporation.

6. Read/Write mode 2: AM = 1, LG1–0 = 001/010/011
Operation Examples:
This mode is used when the data is vertically written at high speed by performing a logical operation
with the original data. It reads the display data (original data), which has already been written in the
GRAM, performs a logical operation with the write data sent from the microcomputer, and rewrites
the data to the GRAM. This mode can read the data during the same access-pulse width (68-system:
enabled high level, 80-system: RD* low level) as for the write operation since the read operation of
the original data does not latch the read data into the microcomputer and temporarily holds it in the
read-data latch. However, the bus cycle requires the same time as the read operation. The write-data
mask function (WM11–0) is also enabled in these operations. After writing, the address counter (AC)
automatically increments by 256, and automatically jumps to the upper-right edge (I/D = 1) or upper-
left edge (I/D = 0) following the I/D bit after it has reached the lower edge of the GRAM.
1) I/D = "1", AM = "1", LG2-0 = "001" (Logical OR)
2) WM11—0 = "FF0"H
3) AC = "0000"H
Write-data mask:
Read data (1):
Write data (1):
Read data (2):
Write data (2):
"0000"H
"0001"H
"AF00"H
Note: 1. The bits in the GRAM indicated by ’*’ are not changed.
* * * * * * * * 0 1 1 1
* * * * * * * * 1 0 0 0
DB11
DB11
1
1
1 0 1 1 1 1 0 0 0 1 1 0
0 0 0 0 1 1 1 1 0 0 0 0
1 1 0 0 0 0 1 1 1 0 0 0
2. After writin to address "AF00"H, the AC jumps to "0001"H.
1 1 1 1 1 1 1 0 0 0 0
0 0 0 1 0 0 1 0 1 0 1
Figure 41 Writing Operation of Read/Write Mode 2
DB0
DB0
Read data (1) + Write data (1)
Read data (2) + Write data (2)
GRAM
55
Logical operation
(OR)
Logical operation
(OR)
1 0 1 1 1 1 0 1 0 1 1 1
1 1 0 0 1 1 1 1 1 0 0 0
HD66765