Specifications

Data sheet

BMA220

Page 47

BST-BMA220-DS003-08 | Revision 1.15 | August 2011 Bosch Sensortec

third parties. BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.

Note: Specifications within this document are subject to change without notice.

I²C read command

I²C read command supports multiple bytes reading. A read command consists of a 1-byte I²C

write phase followed by I²C read phase. The two I²C transmissions must be separated by a

repeated start condition (Sr). The I²C write phase addresses the slave and sends the register

address to be read. After slave acknowledges the transmission, master generates again a start

condition and sends the slave address together with a read bit (R/W = 1). Then master releases

the bus and waits for the data bytes to be read out from slave. After each data byte the master

has to generate an acknowledge bit (ACK = 0) to enable further data transfer.

A NACK (ACK = 1) from master stops the data transferring from slave. Slave releases the bus

so that master can generate a STOP condition and terminate the transmission.

out. Once a new data read transmission starts, the start address will be set to the register

address specified in the latest I²C write command. By default the start address is set at 0x00.

In this way repetitive multi-bytes reads from the same starting address are possible.

Data transferred by Master

Data transferred by Slave

Start R/W ACK ACK

0001011 0 0000010X

Repeat

Start

R/W A CK A CK A CK

0001011 1 XXXXXXXX XXXXXXXX …

ACK ACK

… XXXXXXXX XXXXXXXX …

ACK ACK Stop

… XXXXXXXX XXXXXXXX

Sr 000

Slave Address Register data - address 06hRegister data - address 04h

Data byte Data byte

S 00

Slave Address

Data byte Data byte

Figure 23: I²C multiple bytes read protocol