BU97931FV Datasheet, PDF (7/32 Pages) Rohm – Multifunction LCD Segment Driver

BU97931FV MAX 112 segments (SEG28×COM4)
●Function description
○Command and data transfer method
○3-SPI (3-wire serial interface)
This device is controlled by a 3-wire signal (CSB, SCL, and SD).
First, Interface counter is initialized with CSB=“H".
Setting CSB=”L” enables SD and SCL inputs.
The protocol of 3-SPI transfer is as follows.
Each command starts with Command or Data judgment bit (D/C) as MSB data, followed by data D6 to D0 (this is when
CSB =”L”).
(Internal data is latched at the rising edge of SCL then it is converted to an 8-bit parallel data at the falling edge of the 8th
CLK.)
When CSB changes from “L” to “H”, and at this time sending commands are less than 8 bits, command and data transfer
are cancelled. To start sending command again, please set CSB=”L" and send command continuously.
After sending RAMWR or BLKWR or GPOSET command, this device is in the RAM data input mode. Under this mode,
device can not accept new commands.
In this case, please execute a “H” to “L” transition at CSB, after this sequence the device is released from RAM data input
mode, and can accept new command.
1st byte Command
CSB
2nd byte Command
3rd byte Command
SCL
SD
D/C D6 D5 D4 D3 D2 D1 D0 D/C D6 D5 D4 D3 D2 D1 D0 D/C D6 D5 D4 D3 D2 D1 D0 D/C _D6
Figure 7. 3-SPI Data transfer Format
* 8-bit data, sending after RAMWR command, are display RAM data
* 8-bit data, sending after BLKWR command, are blink RAM data
* SCL and SD can be set to “H” or cleared to “L” during CSB=”H”
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10.Apr.2015 Rev.004