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TSZ02201-0L5L0F300720-1-2

© 2016 ROHM Co., Ltd. All rights reserved.

27.May.2016 Rev.002

www.rohm.com

TSZ22111 • 15 • 001

BU21028FV-M

Host Interface Specification

The BU21028FV-M controller operates as an I2C slave device. At the start of the communication, it receives an address

byte transmitted by the host processor and then then sends back an acknowledgement byte. The host processor can

transmit a command to execute conversion or to access registers only after receiving the acknowledgement for the address

byte. Communication ends when BU21028FV-M receives a stop command.

●Address byte

On the address byte, the slave address for 2-wire interface is written on the upper 7 bits and the READ/WRITE bit is written

on the last bit. The upper six bits of the slave address are fixed to “100000” while the last bit is determined by the “AD0”

input.

Table 1. Serial Interface Slave Address Byte

MSB

D7

D6

D5

D4

D3

D2

D1

LSB

D0

1

0

0

0

0

0

A0

R/W

Bit D1: A0

Slave address bit0 (AD0)

Bit D0: R/W

1=read (reading data)

0=write (writing data)

●Command byte

The operation of BU21028FV-M is dictated by the command byte. The host processor sets CID (D7) to 1 for conversion

function or to 0 for register access.

Table 2. Serial Interface Command Byte 1(CID=1)

MSB

D7

D6

D5

D4

D3

D2

D1

LSB

D0

1

CMSK

PDM

STP

CF

Bit D7: Command Byte ID

1= Command Byte 1(starts the conversion function determined by CF (Bit D6-D3)

Bits D6-D4: CF

Conversion function is selected as detailed below.

Table 3. BU21028FV-M Conversion Function List

CF Description

0x0 Touch screen scan function: X, Y, Z1 and Z2 coordinates and converted.

0x1 NOP

0x2 Auxiliary input converted.

0x3 Reserved

0x4 Free scan function: Drivers status and input of A/D assignment by Host.

0x5 Calibration: Parameters which used dual touch detection calibrated.

0x6 NOP

0x7 NOP

0x8 X+, X- drivers status.

0x9 Y+, Y- drivers status.

0xA Y+, X- drivers status.

0xB NOP

0xC Touch screen scan function: X coordinate converted.

0xD Touch screen scan function: Y coordinate converted.

0xE Touch screen scan function: Z1 and Z2 coordinates converted.

0xF Reserved