HD66765 Datasheet, PDF (57/71 Pages) Hitachi Semiconductor – 396-channel Segment Driver with Internal RAM for 4096-color Displays

HD66765
8. Read/Write mode 4: AM = 1, LG2–0 = 100/101
This mode is used when the data is vertically written by comparing the original data and the set value
of the compare register (CP11–0). 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
compare operation 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 the 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 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-
n ^{left edge (I/D = 0) following the I/D bit after it has reached the lower edge of the GRAM.}
tio _{Operation Examples:}
a _{1) I/D = "1", AM = "1", LG2-0 = "101" (ummatched write)}
ific ^{2) CP11—0 = "530"H}
3) WM11—0 = "000"H
4) AC = "0000"H
c _DB11
DB0
e _{Write-data mask: 0 0 0 0 0 0 0 0 0 0 0 0}
p _DB11
DB0
S _{Compare register:} 0 1 0 1 0 0 1 1 0 0 0 0
ry ^{Read data (1):}
(unmatched)
Compare
operaton
100110010101
C
ina ^{Write data (1):}
101111000110
Conditional
replacement
R
101111000110
Read data (2):
Prelim ^{Write data (2):}
010100110000
110000111000
Compare
operaton
C
Conditional
replacement
R
010100110000
"0000"H 1 0 1 1 1 1 0 0 0 1 1 0 ^{Write data (1)}
"0001"H 0 1 0 1 0 0 1 1 0 0 0 0 Write data (2)
"AF00"H
GRAM
Note: 1. The bits in the GRAM indicated by ’*’ are not changed.
2. After writin to address "AF00"H, the AC jumps to "0001"H.
Figure 43 Writing Operation of Read/Write Mode 4
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