BU9794KV Datasheet, PDF (18/23 Pages) Rohm – For 200 Segment type LCD LCD Segment Driver

● Function description （BU9799KV）
○ Command transfer method
Issue Slave Address (“01111100”) after generate “START condition”.
1byte after Slave Address always becomes command input.
MSB (“command or data judge bit”) of command decide to next data is command or display data.
When set “command or data judge bit”=‘1’, next byte will be command.
When set “command or data judge bit”=‘0’, next byte data is display data.
S Slave address A 1 Command A 1 Command A 1 Command A 0 Command A Display Data … P
Once it becomes display data transfer condition, it cannot input command.
When want to input command again, please generate “START condition” once.
○ Write display and transfer method
This device has Display Data RAM (DDRAM) of 50×4=200bit.
The relationship between data input and display data, DDRAM data and address are as follows;
Slave address
Command
S 01111100 A 0 0000000 _{A a b c d e f g h A i j k l m n o p}
A… P
Display Data
DDRAM address
00
01
02
03
04
05
06
07 ・・・ 2Fh 30h 31h
0a
e
i
m
COM0
1b
f
j
n
BIT
2c
g
k
o
COM1
COM2
3d
h
l
p
COM3
SEG0 SEG1 SEG2 SEG3 SEG4 SEG5 SEG6 SEG7
Data transfer to DDRAM happens every 4bit data.
So It will be finished to transfer with no need to wait ACK.
SEG47 SEG48 SEG49
○ Reset initialize condition
Initial condition after execute Software Reset is as follows.
・ Display is OFF.
・ DDRAM address is initialized (DDRAM Data is not initialized).
・ Refer to Command Description about initialize value of register.
18/22