AD7156 datasheet(23/28 Pages) AD

23 / 28 page

AD7156

Rev. 0 | Page 23 of 28

If a repeated start condition is encountered after the address

pointer byte, all peripherals connected to the bus respond exactly

as outlined previously for a start condition; that is, a repeated

start condition is treated the same as a start condition. When a

master device issues a stop condition, it relinquishes control of

the bus, allowing another master device to take control of the

bus. Therefore, a master wanting to retain control of the bus

issues successive start conditions known as repeated start

conditions.

AD7156 RESET

To reset the AD7156 without having to reset the entire serial

bus, an explicit reset command is provided. This uses a particular

address pointer word as a command word to reset the part and

upload all default settings. The AD7156 does not respond to the

serial bus commands (do not acknowledge) during the default

values upload for approximately 2 ms.

The reset command address word is 0xBF.

GENERAL CALL

When a master issues a slave address consisting of seven 0s

with the eighth bit (R/W) set to 0, this is known as the general

call address. The general call address is for addressing every

device connected to the serial bus. The AD7156 acknowledges

this address and reads in the following data byte.

If the second byte is 0x06, the AD7156 is reset, completely

uploading all default values. The AD7156 does not respond

to the serial bus commands (do not acknowledge) during the

default values upload for approximately 2 ms.

The AD7156 does not acknowledge any other general call

commands.

1 – 7

START ADDR R/W ACK SUBADDRESS ACK

DATA

ACK

STOP

SDA

SCL

Figure 40. Bus Data Transfer

DATA

A(S)

S SLAVE ADDR A(S)

SUB ADDR

A(S)

LSB = 0

LSB = 1

DATA

S SLAVE ADDR A(S)

SUB ADDR A(S) S SLAVE ADDR

A(S)

DATA

A(M)

DATA

WRITE

SEQUENCE

READ

SEQUENCE

A(S) = NO ACKNOWLEDGE BY SLAVE

A(M) = NO ACKNOWLEDGE BY MASTER

A(S) = ACKNOWLEDGE BY SLAVE

A(M) = ACKNOWLEDGE BY MASTER

S = START BIT

P = STOP BIT

A(S)

A(M)

Figure 41. Write and Read Sequences

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