hd66421 Renesas Electronics Corporation., hd66421 Datasheet - Page 24

• Manufacturer Part Number: hd66421
• Description: Ram-provided 160 Channel 4-level Grey Scale Driver For Dot Matrix Graphics Lcd
• Manufacturer: Renesas Electronics Corporation.

Read-Modify-Write:
incremented after reading form or writing data to
the display RAM at normal mode. However, X-
or Y-address is not incremented after reading data
from the display RAM at read-modify-write
mode. The data which is read from the display
RAM may be modified and written to the same
Preliminary
Figure 18 The Flow Chart for Read-Modify-Write
X-
or
Finish Modifying
Set X-address
Set Y-address
dummy read
Read Data
Write Data
START
Y-address
END
yes
is
24
no
Address
incremented
address without re-setting the address. Data
is temporarily latched into a HD66421's
buffer and then output next time a read is
performed in a subsequent cycle. This means
that the dummy read is necessary after every
cycle. This sequence is shown in figure 18.
HD66421