HD66760 Datasheet, PDF (60/105 Pages) Hitachi Semiconductor – 104 X 80-dot Graphics LCD Controller/Driver for 256 Colors

HD66760
7. Read/Write mode 3: AM = 0, LG2–0 = 100/101
This mode is used when the data is horizontally written by comparing the original data and the set value of
compare register (CP7–0). It reads the display data (original data), which has already been written in the
GRAM, compares the original data and the set value of the compare register in byte units, and writes the
data sent from the microcomputer to the GRAM only when the result of the comparison satisfies the
condition. This mode reads the data during the same access-pulse width (68-system: enabled high level,
80-system: RD* low level) as write operation since reading the original data does not latch the read data
into the microcomputer but temporarily holds it in the read-data latch. However, the bus cycle requires the
same time as the read operation. The swap function (SWP) and write-data mask function (WM15–0) are
also enabled in these operations. After writing, the address counter (AC) automatically increments by 1
(I/D = 1) or decrements by 1 (I/D = 0), and automatically jumps to the counter edge one-raster-row below
after it has reached the left or right edges of the GRAM.
Operation Examples:
1) I/D = "1", AM = "0", LG2-0 = "100" (matched write), SWP = "0"
2) CP7–0 = "53H"
3) WM15–0 = "0000"H
4) AC = "000"H
WM15
WM0
Write-data mask: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Compare register:
Read data (1):
CP7
CP0
01 0 100 1 1
Compare
operation
DB15
(Matched) DB0
10 0 110 0 10 10 100 1 1 C
Conditional replacement
Write data (1):
Read data (2):
Write data (2):
Read data (3):
10 1 111 0 00 110 00 0 1
Compare
operation
00 00 11 1 100 00 0 000
C
11 00 00 1 110 00 1 100
(Matched)
Compare
operation
01 0 10 011 10 0 00 11 0
C
R
10 0 11 00 10 110 00 0 1
Conditional replacement
R
00 00 11 1 100 00 0 000
Conditional replacement
Write data (3): 1 1 1 1 0 1 0 0 0 0 0 1 1 1 1 1
R
1 1 1 1 0 1 0 0 1 0 0 0 0 11 0
"0000"H
"0001"H
"0002"H
1 0 0 1 1 0 0 1 0 1 1 0 0 0 0 1 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 10 10 0 1 0 0 0 0 11 0
Matched
replacement of
write data (1)
GRAM
Matched
replacement of
write data (3)
Figure 40 Writing Operation of Read/Write Mode 3